Some historians believe that saffron first came to China with Mongol invaders by way of Persia. Saffron is mentioned in the ancient Chinese medical text "Shennong Ben Cao Jing", believed to be from the 3rd century AD (but attributed to mythological emperor Shennong). Yet the Chinese were referring to saffron as having a Kashmiri provenance. The Chinese medical expert Wan Zhen wrote that "habitat of saffron is in Kashmir, where people grow it principally to offer it to the Buddha". Wan 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."