Plato, Epinomis 983a

ἔμψυχα αὐτὰ λέγομεν, πρῶτον τὸ μέγεθος αὐτῶν διανοηθῶμεν. οὐ γάρ, ὡς σμικρὰ φαντάζεται, τηλικαῦτα ὄντως ἐστίν, ἀλλʼ ἀμήχανον ἕκαστον αὐτῶν τὸν ὄγκον—πιστεῦσαι δʼ ἄξιον· ἀποδείξεσιν γὰρ ἱκαναῖς λαμβάνεται—τὸν γὰρ ἥλιον ὅλον τῆς γῆς ὅλης μείζω διανοηθῆναι δυνατὸν ὀρθῶς, καὶ πάντα δὴ τὰ φερόμενα ἄστρα θαυμαστόν τι μέγεθος ἔχει. λάβωμεν δὴ τίς τρόπος ἂν εἴη τοσοῦτον περιφέρειν ὄγκον τινὰ φύσιν τὸν αὐτὸν ἀεὶ χρόνον, ὅσον καὶ νῦν περιφέρεται.

let us first consider their great size. For they are not actually those small things that they appear to be, but each of them is immense in its bulk; we should do well to believe this, because there are ample proofs of such a conclusion. For we can rightly consider the whole of the sun as larger than the whole of the earth, and all the travelling stars are of amazing size. Let us conclude then whether it can possibly be that any natural force revolves this great mass that is now being revolved, continually and at the same time.