What am I supposed to do with the Scribe's rocks?

Hint 1 of 8:

Look at the rocks in inventory.  They must be important, but they're so
dirty.

Hint 2 of 8:

Is there any water nearby?

Hint 3 of 8:

Wash them in the statue fountain.

Hint 4 of 8:

Assemble the stone pieces into runes.  Each rune is three tiles high.