Plato, Meno 83a

διπλάσιον χωρίον γίγνεσθαι; τοιόνδε λέγω, μὴ ταύτῃ μὲν μακρόν, τῇ δὲ βραχύ, ἀλλὰ ἴσον πανταχῇ ἔστω ὥσπερ τουτί, διπλάσιον δὲ τούτου, ὀκτώπουν· ἀλλʼ ὅρα εἰ ἔτι σοι ἀπὸ τῆς διπλασίας δοκεῖ ἔσεσθαι. ἔμοιγε. οὐκοῦν διπλασία αὕτη ταύτης γίγνεται, ἂν ἑτέραν τοσαύτην προσθῶμεν ἐνθένδε; πάνυ γε. ἀπὸ ταύτης δή, φῄς, ἔσται τὸ ὀκτώπουν χωρίον, ἂν τέτταρες τοσαῦται

do you say we get the double space from the double line? The space I speak of is not long one way and short the other, but must be equal each way like this one, while being double its size—eight square feet. Now see if you still think we get this from a double length of line. I do. Well, this line is doubled, if we add here another of the same length? Certainly. And you say we shall get our eight-foot space from four lines of this length? Yes.