Chinese legends attribute the invention of tea to Shennong 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. In 2016, the discovery of the earliest known physical evidence of tea from the mausoleum of Emperor Jing of Han in Xi'an was reported, indicating that tea from the genus Camellia was drunk by Han Dynasty emperors as early as 2nd century BC. The word tu 荼appears in the Shijing and other ancient texts to signify a kind of "bitter vegetable" (苦菜), and it is possible that it referred to a number of different plants such as sowthistle, 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 state of Ba and its neighbour Shu were later conquered by the Qin, and according to the 17th century scholar Gu Yanwu who wrote in Ri Zhi Lu (日知錄): "It was after the Qin had taken Shu that they learned how to drink tea." 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 (the reign of Emperor Xuan of Han), during which tea was cultivated on Meng Mountain (蒙山) near Chengdu.