There is a record in the geographical annals of the Northern Song Dynasty, The Jade Ring of Taiping: "In the fourth year of Wude (AD 62 1 year), I lived in Yingchuan County, and fell into a hole by mistake. I walked for a day without my head, and I was hungry. I saw millet in the hole!" He also said: "Huan Zi's father (Cao Cao) made officials station fields, built caves in Yingchuan County, and spread them for dozens of miles, so that he could drive chariots and steal the imperial palace, so as not to know the truth?" These historical materials are consistent with folklore.