During emperor Qin Er Shi’s reign, eunuch Zhao Gao rode a deer on an outing with the emperor. The emperor said: “Gao, why are you riding a deer?” Gao said: “(It is) a horse.” The emperor said: “Gao, you are wrong. You are calling a deer a horse.” Gao said: “Your Majesty, you are dismissing my words. Please ask the ministers for their opinions.” (When asked,) half of the ministers said it was a deer, and half said it was a horse. At this moment, the Qin emperor could not be confident with his eyes, and believed the evil minister’s words.
This story was also mentioned in the Records of the Grand Historian (Shiji). In Shiji, the ministers pointed to the animal as deer in order to please the eunuch Zhao Gao, and Zhao was said to have later retaliated on those who referred to it as a horse.