Although its origin is not clear, it is indeed called the king, that is, the aquatic plant of the horse god. We all know that the only means of transportation in ancient times was horses, which shows its importance.
There are two legends about the origin of the third eye of a horse. The first is that during the Spring and Autumn Period, Lu Ban was very good at architecture, and one day he competed with his own sister. He wanted to prove who was better, so he built Zhao Zhouqiao.
After the completion of Zhao Zhouqiao, Lu Ban, who has always been very low-key, was super satisfied with his works, so he was very proud, boasting on the Zhao Zhouqiao that his bridge could carry everything in the world.
If you think about it with your head, you will know that he is bluffing, so some gods can't stand it anymore and come and hit him in the face. That is, Zhang's donkey bears the sun, moon and stars, and naturally cannot bear this kind of power.
So he almost collapsed, and Lu Ban was particularly ashamed, so he dug out one of his eyes and landed as a night pearl. It happened to be picked up by the passing horse king, so it became the third eye of the horse king. In fact, I think this story is still too dramatic, and the times in which the characters live are unreal and inappropriate.
Although it is rumored that today's donkey still bears a hoofprint.
The second rumor is that at that time, the Emperor of Heaven sent four people down to earth, and three of them went against their nature and took bribes privately. Only the horse owner is impartial. The emperor praised his vision and gave him a third eye.