Res Gestae

Now the tips of the bow on both sides are represented by the two Bospori lying opposite to each other, the Thracian[*](At Constantinople.) and the Cimmerian; and they are called Bospori, as the poets say, because the daughter of Inachus,[*](Io; cf. Ovid, Metam. i, 586 ff. A more probable reason is that they were so narrow that an ox could swim across them. Amm. is wrong about the second curve, which extends to the Colchi, while the Cimmerian Bosporus (between the Euxine and the Palus Maeotis) is in the middle of the curve; of. Mela, i. 112, 114; Procop. viii. 6, 14 f.) when she was changed into a heifer, once crossed through them to the Ionian sea.