《左传·昭公·昭公四年》
穆子梦见天塌下来压着自己，要顶不住了，回头一看，见到一个人，黑皮肤，驼背，抠眼睛，猪嘴巴，就喊叫说： 牛，来帮我！ 
梦天压己，弗胜。顾而见人，黑而上偻，深目而豭喙，号之曰 牛助余 ，乃胜之。
Mu Zi dreamt of the sky collapsing and himself being crushed down by it, and he felt that he couldn’t support it. Looking back, he saw a person with black skin, a humpback, squinting eyes, and a pig mouth, and so shouted, “Cow, come and help me out!”