《论衡·卷十七·是应篇》
羊本来有两只角，觟角虎有一只角，形体上与一般的羊有所残缺，还不及同类，有什么神奇呢？
羊本二角，觟角虎一角，体损於群，不及众类，何以为奇？
The sheep originally has two horns and the sheep with one horn has one horn. In the physical form, it is defective compared with the ordinary sheep and is not as good as its kind. What is wonderful about it?