Three Kingdoms: A wise grandson, Cao Wei can last for three generations!

Ma Yunlu's eyes were wide open, bigger than copper bells.

"This...how is this possible?!"

Cao Rui brought out the jar of ice, held it up in front of her, and smiled triumphantly: "How about that? I made ice in summer!"

Ma Yunlu reached out and touched the jar of ice, which made her shiver from the cold.

"Are you... a monster?"

Cao Rui laughed heartily: "I'm not a monster, I'm a genius!"

The news quickly spread throughout the Cao family mansion.

When Zhen Mi arrived, Cao Rui had already made a bowl of chilled mung bean soup with that jar of ice—of course, the mung bean soup was made in the kitchen, but he made the ice.

Zhen Mi took a bite, and her eyes lit up.

"Rui'er, did you really do this?"

Cao Rui nodded and explained the principle of making ice with saltpeter. Zhen Mi was confused, but there was one thing she understood—her son could make ice in the summer.

"Mother, I want to go to the Prime Minister's residence." Cao Rui put down her bowl. "Grandfather needs to know about this."

That evening, Cao Rui took the jar of ice to the Prime Minister's residence.

Cao Cao was reviewing documents in his study, sweating profusely from the heat. When Cao Rui entered, before he could even speak, he noticed that Cao Rui was carrying a jar with white steam rising from its mouth.

"What is this?"

Cao Rui placed the jar on the table and said respectfully, "Grandfather, your grandson has brought you ice."

Cao Cao was stunned for a moment, then reached out and touched it—it was ice cold.

"Where did this come from? The ice at Bingjingtai hasn't been broken yet."

Cao Rui laughed: "It's not from Bingjingtai, it was built by my grandson."

Cao Cao narrowed his eyes.

"Made by yourself? Making ice in the summer?"

Cao Rui explained the principle of making ice with saltpeter again. Cao Cao listened and remained silent for a long time.

Then he stood up, walked to Cao Rui, and bent down to look at him.

"Who taught you this method?"

Cao Rui met his gaze and said frankly, "No one taught me. I heard Yunlu say that Grandfather has an ice well platform where ice is stored in winter for summer use. I wondered if it would be possible to make ice directly in the summer?"

After thinking for a long time, he remembered hearing that saltpeter could cool water. His grandson tried it, and sure enough, it froze.

Cao Cao looked at him, his eyes filled with a mixture of shock, relief, and something else he couldn't quite put his finger on.

After a long while, he straightened up and suddenly smiled.

He walked to the door and ordered the guards outside, "Go and summon Jia Xu, Pang Tong, Xun Yu, and Cheng Yu!"

Soon after, several advisors arrived. They were all stunned when they saw the jar of ice on the table.

Cao Cao pointed to the jar of ice and repeated Cao Rui's words.

After hearing this, everyone turned to look at Cao Rui.

Jia Xu squinted, a slight smile playing on his lips, but remained silent.

Pang Tong walked straight over, squatted down, examined the jar of ice closely, then reached out and touched it, clicking his tongue in amazement: "Good lad, are you trying to reach for the heavens?"

Xun Yu pondered for a moment before speaking, "Prime Minister, if this matter can truly be promoted, the use of ice in the summer will no longer be limited to what is stored in winter. This is a matter that benefits the country and its people."

Cheng Yu nodded: "You are right. Saltpeter can be reused and is not expensive. If it can be widely adopted, people can also enjoy ice in the summer."

Cao Cao stroked his beard, looking at Cao Rui with eyes full of admiration.

"Rui'er, what do you plan to do with this method?"

Cao Rui thought for a moment and said, "I'd like to try making more first. If it works, I'll teach the people in the manor to use it here first. Once it's stable, we can spread it out."

Cao Cao nodded: "Alright. I'll leave this to you. Just tell me what you need."

Cao Rui was overjoyed and cupped his hands in thanks, saying, "Thank you, Grandfather!"

It was already evening when I left the Prime Minister's residence.

Cao Rui hugged the jar of ice and walked home, feeling very happy.

Making ice in summer—this was unique in the Three Kingdoms period. Now, whenever it gets hot, ice can be made anytime. Iced mung bean soup, iced watermelon, iced wine… just thinking about it is wonderful.

Moreover, this thing can make money.

Saltpeter is reusable and inexpensive. If you opened an ice shop, selling ice in the summer and hot drinks in the winter, you'd have business all year round…

As he was thinking, he suddenly heard a voice behind him.

"Cao Rui".

Cao Rui turned around and saw Ma Yunlu.

She stood in the moonlight, still dressed in red, her long hair blowing in the night breeze, a smile in her eyes.

What are you doing here?

"I'll be waiting for you." Ma Yunlu walked over and looked at him. "Your magic trick was really amazing."

Cao Rui chuckled: "It's alright."

Ma Yunlu looked at him, then suddenly reached out and ruffled his hair.

"Tell me, what other skills do you have?"

Cao Rui thought for a moment, then said seriously, "I can also fight. Haven't you seen that?"

Ma Yunlu smiled, a very happy smile.

"Okay, then from now on, if we fight, and you win, I'll make you chilled mung bean soup. If you lose, you make it for me."

Cao Rui nodded: "Deal."

The two walked side by side in the moonlight, neither of them speaking.

Behind him, Xu Hu followed at a distance, a barely suppressed smile on his face.

The next day, Cao Rui began formal research on making ice from saltpeter.

He had Xu Hu buy dozens of kilograms of saltpeter and had more than a dozen earthenware jars brought over, which he then set up in the courtyard.

Ma Yunlu squatted down beside him, watching and occasionally handing him something or offering a helping hand.

Zhen Mi sat on the veranda, holding a needle and thread in her hand, sewing clothes while watching the two children with a smile on her face.

After several attempts, Cao Rui finally figured out the pattern—the ratio of saltpeter to water was roughly one to three. The more saltpeter you added, the faster it would freeze. But you couldn't add too much, as it would actually slow things down.

He also discovered that saltpeter could be reused—by pouring out the frozen saltpeter solution and drying it in the sun, the saltpeter would crystallize out and be reused.

"Yunlu, look!" Cao Rui held up a piece of dried saltpeter, beaming with pride. "This can still be used!"

Ma Yunlu took it and examined it, marveling, "This thing is truly amazing."

Cao Rui put away the saltpeter, then suddenly remembered something.

"Yunlu, do you think we could make money if we opened an ice shop and sold ice in the summer?"

Ma Yunlu paused for a moment, then smiled.

"You? Open a shop? You're the son of the Prime Minister's family, what kind of shop do you open?"

Cao Rui shook his head: "What's wrong, young master? Can't you do business?"

Ma Yunlu looked at him with a complex expression in her eyes.

"Are you really going to do this?"

Cao Rui nodded.

Ma Yunlu thought for a moment and said, "Then you need to find a reliable person to manage it for you. It's not appropriate for you to do it yourself."

Cao Rui's eyes lit up: "Do you have someone suitable?"

Ma Yunlu laughed: "I didn't."

Cao Rui was immediately disappointed.

Upon seeing this, Ma Yunlu couldn't help but burst into laughter.

"What are you laughing at?"

"Cao Rui, Cao Rui, you pride yourself on being clever, yet you can't think of a suitable person. Have you forgotten what your aunt used to do?"

Cao Rui's eyes lit up. That's right, how could he have forgotten about Zhen Mi?