As for cement, it wasn’t hard. Limestone, clay, sand—if some iron slag could be added, even better. The proportions could be worked out through trial and error. Or, to go all the way, use sticky rice mortar, which was more in line with current craftsmanship. That stuff was strong, waterproof, durable, could be used for building walls and paving roads, and was cheap. But Lin Yi didn’t know if such a method already existed in this era.
Thinking of this, she turned her head and asked casually, “Husband, have you ever heard of sticky rice mortar?”
"Huh?" Gu Fang was momentarily taken aback, then looked a bit embarrassed. "The name suggests it’s related to construction. I know very little about that."
"You guessed its use right away—you’re clever!" Lin Yi immediately beamed and gave him a thumbs-up. She’d gotten used to asking him everything, forgetting he was a military commander, not a builder. Seeing a hint of shyness in his expression, her heart softened. She explained gently, "It’s a building material. You cook sticky rice into a thick paste, strain it, mix it with slaked lime and sand, and you get a very strong, waterproof material. It can be used for roads, walls, even city walls, and it’s cheap."
Gu Fang listened, curiosity flickering in his eyes. "That useful? I know slaked lime—it’s often used by commoners to tamp earth for walls. But I’ve never heard of sticky rice mortar."
"Husband, why not give it a try?" Lin Yi’s eyes sparkled, her tone light. "Once this material is made and laid out, it should dry in about five hours. If we start today, we might see results before nightfall."
Gu Fang was curious whether cement was as strong as Lin Yi claimed, so he naturally agreed. Lin Yi then called A Fu over and asked him to send for Xiao Zhu. Although A Fu and the others were reliable, in Lin Yi’s heart, Xiao Zhu was the one who best understood her ideas. Making cement was simple; the key was the proportions. She didn’t need to supervise personally—it was perfect to hand it over to Xiao Zhu, especially since Xiao Zhu had no urgent tasks now.
True to form, riding a horse was much faster than a carriage. In less than two quarters of an hour, Xiao Zhu had nimbly arrived beside the carriage. Seeing Lin Yi, she took out some snacks she’d prepared from her sleeve and handed them over, then leaned in and whispered, “Madam, do you have any orders?”
"Mm, there’s something I need you to do." Lin Yi happily accepted the snacks, divided them into three portions, intending to share them with Gu Fang and Xiao Zhu. Xiao Zhu quickly waved her hand, declining, saying she’d already eaten, so Lin Yi cheerfully kept both portions. As she ate, she instructed, “I want you to try making cement. Remember: first cook sticky rice into a thick porridge, strain out the grains, and keep the thick liquid—that’s the sticky rice slurry. Then take slaked lime, sticky rice slurry, and sand, and mix them in a ratio of five parts, two parts, and three parts.”
Xiao Zhu silently repeated it, then nodded. “Miss, I’ve got it. What should I do after the cement is made?”
Seeing that she remembered well, Lin Yi continued. “Find a bare piece of wasteland with no grass or debris. First, lay a layer of broken stones as a base, then spread the cement on top. Note that the cement layer should be at least two fen thick. Smooth the surface, then let it sit for five hours without anyone stepping on it.”
“Yes.” Xiao Zhu agreed, then asked, “How large should the cement be? Where should I choose the wasteland?”
Lin Yi thought for a moment. She intended it for road paving, so she’d go with road dimensions. “Make it about as wide as a regular road. As for length, just enough for several of us to walk a few steps—you decide.” She paused, then turned to Gu Fang. “Husband, where do you think is suitable?”
Gu Fang considered briefly. “It might be better to do it in a manor. I happen to own a village east of the city. How about we try it there?”
“Great, it’s on the way.” Lin Yi nodded happily. “Xiao Zhu, come with us. You can go ahead to the village and get started while we visit the workshop.”
Half an hour later, A Fu reported from outside the carriage that the road to the village diverged from the road to the workshop. Xiao Zhu then went ahead to the village with the servants A Fu had sent.
After Xiao Zhu left, Gu Fang said to Lin Yi, “That village is quite a distance from the mansion, and the road-paving project is no small task—it’ll take a while. How about we go see the results tomorrow?”
“Sounds good.” Lin Yi had been thinking the same. She hadn’t considered the experimental area carefully; she’d thought they could test it in the General’s Mansion, but then realized that land was precious in the Imperial City and the mansion didn’t have such open space.
Seeing her agreement, Gu Fang added gently, “This village happens to be not far from Prince Ning’s mansion. The day after tomorrow, we’ll meet Prince Ning. If the cement we see tomorrow is as solid as you say, we could report it to him as well. If he wants to inspect it in person, it’ll be convenient.”
Lin Yi was slightly taken aback. She hadn’t expected that before even seeing the cement, Gu Fang had already thought this far. She looked up at him, surprise in her eyes.
Gu Fang met her gaze and chuckled. “What is it?”
“Nothing,” Lin Yi said honestly. “Just a bit surprised.”
Gu Fang raised an eyebrow, intrigued. “What surprises Xiaoyi?”
“A lot of things.” Lin Yi counted on her fingers. “For example, I only told you what cement is, but you haven’t even seen it yet, and you’re already thinking of presenting it to Prince Ning. Also, His Majesty treated you so badly, but you haven’t transferred any of that resentment to Prince Ning.” If she hadn’t known this was a world from a book, and that the plot couldn’t change drastically—Prince Ning would eventually take the throne—she might have been tempted to advise him to rebel.
Gu Fang was silent for a moment before replying slowly, “I can see how capable Xiaoyi is. When you speak of these novel things, your eyes are steady and without hesitation—that’s the confidence of someone who knows her stuff. Besides, I always want to see the cement’s effectiveness with my own eyes before making a decision. Even if it doesn’t meet expectations, I’ll just keep quiet about it.” He paused, a faint hint of sarcasm in his voice. “As for resentment… I naturally resent His Majesty. But Prince Ning is not His Majesty, and though he seems glamorous now, he’s had a hard time in the past.”
Lin Yi was secretly impressed. Truly worthy of someone who commands troops—he’d taught himself microexpressions to detect lies. She couldn’t help but ask curiously, “So do all people in high positions, like you, read people’s expressions and distinguish truth from falsehood?”
“Nine out of ten do.” Gu Fang nodded. “Heads of noble families, powerful court officials, wise rulers, and even generals like me—knowing people is the most basic and most crucial skill.”
Lin Yi understood this principle. Many in high positions achieved great things precisely because they knew people and appointed them wisely. But she still had a question. “Then why do so many wise emperors in history become obsessed with alchemy and elixirs in their later years? With their ability to judge people, couldn’t they see it was a fraud?”
Gu Fang was visibly taken aback, a rare look of confusion crossing his face. “Elixirs are fake?”
Huh? His reaction—did he believe in them too? Lin Yi was even more puzzled. “History books record many emperors obsessed with alchemy, and in the end they all…”
“All the emperors recorded in history books eventually died.” Gu Fang interjected gently, his tone calm and without apparent criticism, as if stating a simple fact.
Lin Yi was momentarily speechless. That logic was like saying “everyone who drinks water will die.” She knew the scientific principle behind elixirs causing death and had seen records in historical texts that most elixir takers didn’t live long. But Gu Fang might genuinely think elixirs worked, after all, everyone dies eventually.
After a moment’s thought, Lin Yi changed her approach. “So by saying that, do you believe elixirs are effective?”
Gu Fang was silent for a moment, then nodded. “When I was first injured, the pain was excruciating, and I couldn’t sleep at night. Director Huang of the Imperial Hospital prescribed me a Tranquility Powder. After taking it, I could indeed rest for a while.”
Tranquility Powder?!
Lin Yi’s heart skipped a beat. That was a common prescription containing lead and mercury! She pressed urgently, “Husband, besides the Tranquility Powder, have you taken any other elixirs?” As soon as she said it, she realized that wasn’t helpful. “No, just naming the medicine doesn’t help since I don’t know the ingredients. Do you know if any of the medicines you took contained cinnabar?”
She remembered clearly: cinnabar was still used as a medicinal ingredient today, said to calm the mind and treat fright. But it was actually mercury sulfide, a heavy metal! People fell unconscious from poisoning—no wonder they slept!
Gu Fang looked troubled, but answered in a low voice, “The Tranquility Powder I took did contain cinnabar.”
Great, lead and mercury both present. That Tranquility Powder was generously formulated—as if they were afraid you wouldn’t sleep. Lin Yi’s heart sank, but she held onto one last hope. “How long did you take it?”
Gu Fang thought for a moment and said firmly, “Ten days.”
Still okay, still okay. The dose determines the poison. Ten days’ worth—both lead and mercury—while they had accumulated, as long as he stopped ingesting them, most could be metabolized over time, and the harm would be negligible. Lin Yi breathed a sigh of relief, then said seriously, “Husband, remember this: you must never take these medicines again. They are highly toxic with long-term use.”
Gu Fang agreed without hesitation, but still looked uncertain. “Xiaoyi says it’s highly toxic, but many people around me also take this powder, and they all say it works well.”
The Tranquility Powder was so widespread? Lin Yi’s expression became even more serious. “What I’m about to say—if you don’t understand, ask me anytime.”
“Alright.” Gu Fang agreed.
“The toxicity of Tranquility Powder mainly comes from lead and mercury. Both are heavy metals—metals with high density. Most such metals are toxic and shouldn’t be ingested into the body.” Lin Yi tried to explain in terms he could understand. “For example, lead is widely used now: lead dan and lead cream as medicine, lead powder as makeup, lead vessels to enhance flavor. But it damages the nervous system, blood system, and kidneys. Mercury, commonly found in cinnabar and qingfen, destroys the nervous system, skin, reproductive system, and urinary system.”
Gu Fang lowered his eyes in thought, then looked up. “These ‘systems’ you mention—do they refer to parts of the body? And the damage—does it manifest as headaches, fatigue, and such?”
“Exactly.” Lin Yi was surprised by his keenness. “Headaches, dizziness, fatigue, tinnitus or hearing loss, hallucinations, blurred vision, stumbling, uncoordinated movements, slurred speech, slow thought, insomnia with many dreams, trembling hands and feet—these are symptoms of nervous system damage. As for damage to other systems, they mostly show as nausea, vomiting, abdominal pain, diarrhea, scanty or no urine, itching, rashes, sores, coughing, chest tightness, difficulty breathing, and even difficulty having children.” She looked at Gu Fang. “Husband, you mentioned headaches and fatigue—have you seen such cases?”
“Mm.” Gu Fang nodded. “Many of my colleagues have old injuries. When the pain is unbearable, they take Tranquility Powder. Among those who take it heavily, some indeed show headaches and fatigue.”
On hearing this, Lin Yi couldn’t help but be astonished. “Since these symptoms have appeared, why hasn’t anyone suspected the Tranquility Powder?”
At this, a hint of embarrassment crossed Gu Fang’s face, and he said in a low voice, “Because so many have these symptoms, we all thought it was just a result of getting older.”