《搜神记·卷二十》
到后来，孔愉因为讨伐华轶的功劳而被封为馀不亭侯，工人为他浇铸官印，印纽上的乌龟老是向左回望，浇铸了多次还是象原来样子。铸印工把这事报告给了孔愉，孔愉才意识到这次封侯是乌龟的报答，于是就拿了印佩带在身上。
及后，以功封余不亭侯，铸印，而龟钮左顾，三铸，如初，印工以闻，愉乃悟其为龟之报，遂取佩焉。
Later, Kong Yu was enfeoffed as the Marquis of the Yu Bu Pavilion for his contribution in suppressing Hua Yi. When the artisans cast an official seal for him, the turtle knob on the seal kept facing the left. Even after several attempts, it still looked the same. The seal casters reported this incident to Kong Yu. Kong Yu then realized that this enfeoffment was a form of repayment from the tortoise. He took the seal and wore it on his body.