Man shouldn't be able to see his own face - there's nothing more sinister. Nature gave him the gift of not being able to see it, and of not being able to stare into his own eyes.
Only in the water of rivers and ponds could he look at his face. And the very posture he had to assume was symbolic. He had to bend over, stoop down, to commit the ignominy of beholding himself.
The inventor of the mirror poisoned the human heart.