Plato, Laws 809c

παίδων ἐπιμελητά, τοὺς ὑπὸ σοῦ τρεφομένους, οὐκ εἰρήκαμεν. καίτοι τὰ μὲν περὶ τὸν πόλεμον ἃ δεῖ μανθάνειν τε αὐτοὺς καὶ μελετᾶν ἔχεις τῷ λόγῳ, τὰ δὲ περὶ τὰ γράμματα πρῶτον, καὶ δεύτερον λύρας πέρι καὶ λογισμῶν, ὧν ἔφαμεν δεῖν ὅσα τε πρὸς πόλεμον καὶ οἰκονομίαν καὶ τὴν κατὰ πόλιν διοίκησιν χρῆναι ἑκάστους λαβεῖν, καὶ πρὸς τὰ αὐτὰ ταῦτα ἔτι τὰ χρήσιμα τῶν ἐν ταῖς περιόδοις τῶν θείων, ἄστρων τε πέρι καὶ ἡλίου καὶ σελήνης, ὅσα διοικεῖν ἀναγκαῖόν ἐστιν περὶ

You know from our discourse what are the military exercises they ought to learn and to practice, but the matters that have not as yet, my friend, been fully declared to you by the lawgiver are these—first, literature, next, lyre-playing; also arithmetic, of which I said that there ought to be as much as everyone needs to learn for purposes of war, house-management and civic administration; together with what it is useful for these same purposes to learn about the courses of the heavenly bodies—stars and sun and moon—in so far as every State