《旧唐书·列传·卷二十一》
从前汉文帝时，有个献千里马的人，文帝对他说：我不顺利每天走三十里，顺利每天走五十里，銮车在前，跟着的车在后，我单独乘千里马将走到哪里去呢？
昔汉文有献千里马者，曰：吾凶行日三十里，吉行五十里，銮舆在前，属车在后，吾独乘千里马将安之？
In times past, in the reign of Emperor Wen of Han, there was a man who presented the emperor with a horse that could run a thousand li a day; Emperor Wen said to him: "In bad times I travel thirty li a day, in good times I travel fifty li a day; the imperial carriage is in front, and the rest of the entourage follows behind; if I were to ride this thousand-li horse alone, where would I go?"