Some historians believe that saffron first came to China with Mongol invaders by way of Persia. On the other hand, saffron is mentioned in ancient Chinese medical texts, including the forty-volume "Shennong Bencaojing" (神農本草經—"Shennong's Great Herbal", also known as "Pen Ts'ao" or "Pun Tsao") pharmacopoeia, a tome dating from 200–300 BC. Traditionally attributed to the legendary "Yan" ("Fire") Emperor (炎帝) Shennong, it documents 252 phytochemical-based medical treatments for various disorders. Yet around the 3rd century AD, the Chinese were referring to saffron as having a Kashmiri provenance. For example, Wan Zhen, a Chinese medical expert, reported that "[t]he habitat of saffron is in Kashmir, where people grow it principally to offer it to the Buddha." Wan also reflected on how saffron was used in his time: "The [saffron crocus] flower withers after a few days, and then the saffron is obtained. It is valued for its uniform yellow colour. It can be used to aromatise wine."