begun in the region of Yunnan, where it was used for medicinal purposes. It is also believed that in Sichuan, "people began to boil tea leaves for consumption into a concentrated liquid without the addition of other leaves or herbs, thereby using tea as a bitter yet stimulating drink, rather than as a medicinal concoction." Chinese legends attribute the invention of tea to the mythical Shennong (in central and northern China) in 2737 BC, although evidence suggests that tea drinking may have been introduced from the southwest of China (Sichuan/Yunnan area). The earliest written records of tea come from China. The word tú appears in the Shijing and other ancient texts to signify a kind of "bitter vegetable" (), and it is possible that it referred to many different plants such as sow thistle, chicory, or smartweed, as well as tea. In the Chronicles of Huayang, it was recorded that the Ba people in Sichuan presented tu to the Zhou king. The Qin later conquered the state of Ba and its neighbour Shu, and according to the 17th century scholar Gu Yanwu who wrote in Ri Zhi Lu (): "It was after the Qin had taken Shu that they learned how to drink tea." Another possible early reference to tea is found in a letter written by the Qin dynasty general Liu Kun who requested that some "real tea" to be sent to him. The earliest known physical evidence of tea was discovered in 2016 in the mausoleum of Emperor Jing of Han in Xi'an, indicating that tea from the genus Camellia was drunk by Han dynasty emperors as early as the second century BC. The Han dynasty work, "The Contract for a Youth", written by Wang Bao in 59 BC, contains the first known reference to boiling tea. Among the tasks listed to be undertaken by the youth, the contract states that "he shall boil tea and fill the utensils" and "he shall buy tea at Wuyang". The first record of tea cultivation is also dated to this period, during which tea was cultivated on Meng Mountain () near Chengdu. Another early credible record of tea drinking dates to the 3rd century AD, in a medical text by Hua Tuo, who stated, "to drink bitter t'u constantly makes one think better." However, before the Tang dynasty, tea-drinking was primarily a southern Chinese (Southern dynasties) practice centered in Jiankang. Tea