My house's electrical wiring dates back to the Tang Dynasty.

"Huai Dao, your father is reminding you that you must not tell anyone about what your Uncle Li taught in class, not even me. You must keep it to yourself." Qin Shubao thought that his son, as the Crown Prince's study companion, would definitely have to attend Hongwen classes with the Crown Prince. Li Mingbo's identity was special, and the content he taught would definitely be knowledge from more than 1,300 years in the future. Only the Crown Prince knew these things. Even if they studied together, they could only understand them themselves and could not pass them on to outsiders.

"Yes, I will obey my father's words."

"You must listen carefully to your Uncle Li's lessons. If I hear you're not paying attention, I'll beat you to death when I get back."

The same thing happened at Cheng Yaojin's residence in Huai De Fang.

However, Comrade Cheng Chumo was not as lucky as Qin Huaidao.

Cheng Chumo could only sit on the side and watch his father eat roast duck and drink wine from the transparent glass bottle.

Comrade Cheng Chumo sat to one side, the aroma of the wine wafting towards him, swallowing hard, but he dared not reach out.

Perhaps feeling a pang of pity, Cheng Yaojin picked up a piece of roast duck and handed it to his eldest son.

Comrade Cheng Chumo then tasted a piece.

The aroma of meat is irresistible. The meat is bright red on the outside and tender and juicy on the inside.

Cheng Chumo finished eating in an instant and looked at the plate of roast duck on the table.

"This was made at Hongwen Mansion, so there will be plenty of opportunities to eat it in the future," Cheng Yaojin said.

"Father, what does that mean?" Cheng Chumo perked up immediately when he heard that he would have the chance to eat it in the future.

"Tomorrow morning, go to your Uncle Qin's residence and find Huai Dao. Find a large plot of land in Pingkang Ward and open a roast duck restaurant with Hong Wen and the rest of us. We'll specialize in this kind of roast duck. Be serious about it. His Majesty is involved in this. This is His Majesty's decree. If you don't do it well, I'll break your legs."

So, does that mean I can eat as much as I want in the future?

Upon hearing this, Comrade Cheng Chumo imagined eating such roast duck every day in the future, and his future looked bright.

"Don't worry, Dad, I promise I'll handle it perfectly!"

After Li Mingbo saw the guests off, Lianhua came over.

Li Mingbo told Lianhua that Li Shimin had agreed to let her marry him and that her status had been changed to that of a respectable woman.

"I thank you for your kindness, my lord," Lotus said, her eyes reddening as she bowed.

"The date is set for the third day of the ninth month."

In ancient times, marrying a wife was not the same as taking a concubine. Marrying a wife involved going through six rites and other complicated procedures.

Fortunately, the Duke of Yi's wife, Lady Sun, helped with this matter.

Li Mingbo brought Lianhua back to the study.

Li Mingbo sat down and started writing with a ballpoint pen.

This is the method of salt production.

I plan to open a roast duck restaurant in the future, which will require a lot of salt.

The salt produced in the Tang Dynasty was refined salt, but it did not meet the requirements. It contained many impurities, tasted bitter, and was even poisonous, affecting its flavor.

Therefore, Li Mingbo wanted to make salt.

The method is simple: melt, filter, steam, and solidify.

He drew up the tools and asked the steward, Old Zhao, to forge them, and also to buy some mineral salt that looked poisonous.

We need to test whether it works first before submitting it to Li Shimin.

During the Tang Dynasty, salt mainly consisted of sea salt, well salt, pond salt, and granulated salt.

Sea salt is salt produced by evaporating seawater and is mainly produced in the coastal areas of the Yangtze and Huai River regions.

Well salt is extracted from underground brine through drilling, and is mainly produced in Jiannan Road;

Lake salt is salt that is naturally evaporated or sun-dried from surface saltwater lakes, and is mainly produced in the Hedong region.

There is another type called cliff salt or rock salt, which is actually mineral salt. The main production areas are Lingzhou in Ningxia Yanchi Mountain in the northwest and Xizhou in Sichuan Yanyuan in the southwest.

Regardless of the type of salt, it wasn't filtered to remove impurities, so it tastes somewhat bitter.

Moreover, the colors are varied; for example, pond salt has a reddish tinge.

I was supposed to return to the modern world tomorrow, but I'll make the salt first and hand it over to Li Shimin.

This is a big deal.

It was a small matter for Li Mingbo, but a big deal for the people of the Tang Dynasty.

If it can be widely promoted, it can benefit the poor people of the world.

First, the filtration equipment.

This is the core technology.

At the bottom is fine linen; on top of the linen is charcoal, which absorbs odors and dissolved substances; above the charcoal is clean fine sand, and on top of that is larger sand.

The larger pebbles at the top filter out larger impurities.

Beneath the large pebbles lies clean, fine sand. This fine sand filters out the mud and impurities that fall from above, some of which are slightly smaller than the pebbles.

The third layer is charcoal. Charcoal can effectively absorb odors and dissolve toxic substances.

The fourth layer is fine linen.

The entire filter is made in a funnel shape.

Crush the cheapest, already dissolved salt grains, dissolve them in water, and then filter them out until the salt water looks clean and clear.

The salt is steamed in an earthenware pot to make snow salt, and then crushed into a finer salt.

Then, the finished product, along with the tools and the production process, were brought to the palace and handed over to Li Shimin.

After seeing the finished product, Li Shimin summoned Wu Hai to prepare it.

After Wu Hai quickly finished preparing, Li Shimin watched as Li Mingbo operated the equipment. The finished product was just as clean as the one Li Mingbo had brought. Li Shimin happily turned around and returned to Ganlu Hall.

"Hongwen, with your method, we will no longer have to eat poisonous salt. We can produce a continuous supply of tribute-grade refined salt, and the people of the world can also eat this kind of salt. In particular, in future wars, the soldiers at the front will also be able to eat salt and have strength, instead of relying on vinegar and cloth," Li Shimin said excitedly.

Li Shimin classified the filtration technology as the highest level of secrecy, allowing it to be mastered only by the Imperial Salt Administration.

As for how to do it, Li Mingbo didn't care. He figured that with Li Shimin's intelligence, he would definitely make good use of this technology.

To prevent the risk of technology leakage, Li Mingbo stopped making salt himself, and Li Shimin promised to give priority to the Chang'an Roast Duck Restaurant.

I was supposed to go back to Hyundai today, but I need to finalize the location for the roast duck restaurant before I go back.

Once the location is decided, then hire someone to do the renovations.

Li Mingbo left the palace, arrived at Yanxi Gate, and boarded his own carriage.

"Ah Lang, where are we going now? Back to the manor?" Old Zhao, sitting at the front of the carriage, turned to look at Li Mingbo inside, holding the reins.

"Let's go take a look at Pingkangfang," Li Mingbo said.

The carriage traveled south along the eastern wall of the imperial city and arrived at Pingkang Ward, the southeast corner of the imperial city.

Pingkangfang is famous for its entertainment.

The northwest corner of Pingkangfang was Chang'an's red-light district.

There is an official Zuo Jiao Fang, an official music organization.

A three-story wooden structure.

The Bodhi Temple, a poetry academy of the imperial palace, was built in the second year of the Kaihuang era of the Sui Dynasty in the southwest corner and was rebuilt in the fifth year of the Zhenguan era.

"Old Zhao, which minister resides in Pingkang Ward?" This was Li Mingbo's first time visiting Pingkang Ward. Looking at the bustling crowds on the main street, he lifted the curtain and asked Old Zhao, who was driving the carriage.

On either side of the carriage, Wang Chao, Ma Han, Zhang Long, and Zhao Hu stood guard, each holding a Tang sword.

They were wearing bulletproof vests, stab-proof gloves, and black military boots.