Qizi cake is the most representative embodiment of Pu 'er tea. Pu 'er tea is named after Pu 'er House, and Pu 'er tea is famous all over the world through the ancient tea-horse road. Pu 'er House was named as early as the 14th year of Hongwu in Ming Dynasty (1381), and the place name "Pu 'er" was first used in official documents. Pu 'er became an important market town for producing, processing and distributing tea at that time. The steamed green, fried green, sun-dried green group tea and loose tea have won the favor of many merchants. During the Wanli period, the court set up a government office in Pu 'er to manage the tea trade, and the government officials transported the tea in Pu 'er tea area to Beijing and presented it to the palace. Pu 'er tea began to get its name and became popular all over the world. There is a saying in Xie Zhao's "A Brief Introduction to Yunnan" that "all the sugarcane used in the world is popular with tea". "Round as the bright moon in Sanqiu, fragrant in the blue of nine fields." This is the sacred metaphor of Emperor Qianlong for Qizi cake. Pu 'er pressed tea was born in a special geographical environment and special time. In the old weights and measures, there were sixteen taels per catty, which was for the convenience of transportation. Pu 'er tea is "steamed and agglomerated, and pressed and molded." Because seven pieces weigh one piece, seven pieces are packed in a tube (bamboo shoot shell package). Qizi cake got its name, and now it is equivalent to 357 grams per piece of weights and measures. Qizi cake tea, which looks like a full moon, is a traditional export variety of Yunnan and sells well in Hong Kong, Macao and Southeast Asia. In the past, ethnic groups and their children had to send seven cakes in marriage. According to legend, overseas Chinese living in Southeast Asia are now very popular. Why do seven cakes only contain seven cakes instead of eight or six? One theory is that Qizi cake tea was originally obtained from border trade since the Tang Dynasty. Referred to as Tea Horse Market for short, when trading, seven cakes were tied up and one cake was added, and eight pieces were counted. What's the other separated cake for? It's used to pay taxes. There is another saying: a cake of tea is 357 grams, and a tube of seven cakes; 357 grams *7 cakes of tea =2499 grams, about 2.5 kilograms. A piece of 12 tubes is about 3 kilograms. A horse carries two pieces, about 6 kilograms, which is just enough to carry the load. The ancestors have already calculated that this is how the caravan transported tea in the old days.