In the 1st century during the Han dynasty, fresh lychees were a popular tribute item, and in such demand at the Imperial Court that a special courier service with fast horses would bring the fresh fruit from Guangdong. There was great demand for lychee in the Song Dynasty (960-1279), according to Cai Xiang, in his "Li chi pu" (Treatise on Lychees). It was also the favourite fruit of Emperor Li Longji (Xuanzong)'s favoured concubine Yang Yuhuan (Yang Guifei). The emperor had the fruit delivered at great expense to the capital.