《宋书·志·卷三十二》
义熙年间，宫城墙上、专供皇上车驾通行的御道左右都长出蒺藜。这是草妖。
义熙中，宫城上御道左右皆生蒺藜，草妖也。
During the Yixi years, caltrops grew on both sides of the Imperial City wall and on the royal road reserved for the emperor's carriage. This was an evil omen.