《太平广记·卷十一·神仙十一》
曹操下令逮捕左慈，左慈钻进羊群中，追捕他的人分不清，就查羊的原数，果然多出了一只，知道左慈变成了羊。
乃敕收慈，慈走入群羊中，而追者不分，乃数本羊，果余一口，乃知是慈化为羊也。
Cao Cao ordered the arrest of Zuo Ci. Zuo Ci snuck into a herd of sheep, and those pursuing him could not tell him apart. So they counted the original number of sheep, and indeed there was one more. They knew Zuo Ci had changed into a sheep.