Plato, Meno 82c

τετράγωνον χωρίον ἴσας ἔχον τὰς γραμμὰς ταύτας πάσας, τέτταρας οὔσας; πάνυ γε. οὐ καὶ ταυτασὶ τὰς διὰ μέσου ἐστὶν ἴσας ἔχον; ναί. οὐκοῦν εἴη ἂν τοιοῦτον χωρίον καὶ μεῖζον καὶ ἔλαττον; πάνυ γε. εἰ οὖν εἴη αὕτη ἡ πλευρὰ δυοῖν ποδοῖν καὶ αὕτη δυοῖν, πόσων ἂν εἴη ποδῶν τὸ ὅλον; ὧδε δὲ σκόπει· εἰ ἦν ταύτῃ δυοῖν ποδοῖν, ταύτῃ δὲ ἑνὸς ποδὸς μόνον, ἄλλο τι ἅπαξ ἂν ἦν δυοῖν ποδοῖν τὸ χωρίον;

Now, a square figure has these lines, four in number, all equal? Certainly. And these, drawn through the middle, are equal too, are they not? Yes. And a figure of this sort may be larger or smaller? To be sure. Now if this side were two feet and that also two, how many feet would the whole be? Or let me put it thus: if one way it were two feet, and only one foot the other, of course the space would be two feet taken once ? Yes.