《史记·七十列传·张丞相列传》
张苍担任丞相十几年之后，鲁国有个人叫公孙臣，他上书给皇帝，说汉朝属于土德旺盛时期，其征兆是不久将要有黄龙出现。
苍为丞相十馀年，鲁人公孙臣上书言汉土德时，其符有黄龙当见。
After Zhang Cang had been prime minister for more than ten years, a man from the State of Lu named Gongsun Chen wrote to the emperor that the Han Dynasty was flourishing in the era of the soil, and the omen was that a yellow dragon would appear soon.