Solon, fr. 29 West

πολλὰ ψεύδονται ἀοιδοί.

Poets tell many lies.

This is quoted as a proverbial expression (παροιμία) by Aristotle (Metaphysics 1.2); the idea of poets as liars goes right back to the Muses’ famous address to Hesiod at Theogony 26-28 (which will be coming up soon!).