Translation Request - LUNATIC Mode

The rock on the left clearly says something, but I can't for the life of me make it out.

AverageRenMariFan said in comment #2612311:

The rock on the left clearly says something, but I can't for the life of me make it out.

It's the motto of the RL school Kitauji is based on: さとく（聡く）さやかに（清かに）たくましく（逞しく）.

Edit: I put in a very basic TL. Anyone feel free to editorialize it.

Also present in the anime, though I can't get a clear, high-res screencap right now.