《水经注·卷二》
天马的奇处是有角，所以汉武帝《天马之歌》说：天马来呵，驰过无草之地，沿着东道呵，奔驰千里。
故汉武帝《天马之歌》曰：天马来兮历无草，径千里兮循东道。
The strange thing about the heavenly horse is that it has horns, so Emperor Wu's "Song of the Heavenly Horse" says: The heavenly horse comes, galloping across the grassless land, along the east road, galloping thousands of miles.