When Zhao Kuangyin, the ancestor of the Song Dynasty, was not yet emperor at first, he was a general under Chai Rong of Later Zhou Shizong, and Cao Bin was a waiter at Sejong's side at that time, in charge of tea and wine.
Cao Bin
Zhao Kuangyin once asked Cao Bin for wine to drink, and Cao Bin said: "This is a special wine in the palace, you can't give it to others casually, if you want to drink, you can buy it yourself!" Later, when Zhao Kuangyin became emperor, he once said to his courtiers: "The officials under Zhou Shizong do not deceive the lord, only Cao Bin is alone." Therefore, He regarded Cao Bin as a confidant.
It was still a matter of the Later Zhou Dynasty. When Zhao Kuangyin captured the city of Chuzhou, Later Zhou Shizong ordered Dou Yi to register the money and goods of the government. After a few days, Zhao Kuangyin called his cronies to come and get the silk in the warehouse. Dou Yi said, "When you first captured this city, even if you took away all the belongings in the library, who would dare to say anything?" Now that it is registered, it is all public property, and it must not be taken out without the emperor's edict. Later, after Zhao Kuangyin became emperor, he repeatedly praised Dou Yi for his integrity and planned to appoint him as prime minister.
Sinus instrument
After Dou Yi died, Zhao Kuangyin sighed and said to the ministers around him, "Why did Heaven take away my Dou Yi so quickly?" "I especially regret not reusing the sinus instrument earlier."