《梦溪笔谈·艺文一》
穆、张曾一同参加朝会，在东华门外等待天亮。正讨论古文章法，恰好看到有一匹奔马踏死了一条犬，二人于是相约各描述其事，以比较各自的工拙。
穆、张尝同造朝，待旦于东华门外，方论文次，适见有奔马践死一犬，二人各记其事，以较工拙。
Mu and Zhang once attended a court meeting together and waited for dawn outside the gate of Donghua. While discussing the writing method of ancient prose, they happened to see a galloping horse trample a dog to death, so the two made an appointment to describe the incident to compare their skills.