Plato, Laws 821b

παντάπασι φίλον, οὐδενὶ δὴ τρόπῳ δυνατόν ἐστιν ἔτι μὴ φράζειν. εἰκότα λέγεις· ἀλλʼ ἄστρων πέρι μάθημα τί τοιοῦτον ἀνευρήσομεν; ὦ ἀγαθοί, καταψευδόμεθα νῦν ὡς ἔπος εἰπεῖν Ἕλληνες πάντες μεγάλων θεῶν, Ἡλίου τε ἅμα καὶ Σελήνης. τὸ ποῖον δὴ ψεῦδος; φαμὲν αὐτὰ οὐδέποτε τὴν αὐτὴν ὁδὸν ἰέναι, καὶ ἄλλʼ ἄττα ἄστρα μετὰ τούτων, ἐπονομάζοντες πλανητὰ αὐτά.

he cannot possibly refrain any longer from declaring it. That is reasonable; but what science of this kind shall we find on the subject of stars? At present, my good sirs, nearly all we Greeks say what is false about those mighty deities, the Sun and Moon. What is the falsehood? We assert that they, and some other stars along with them, never travel along the same path; and we call them planets.