Strabo Geography 9.1.1

[1] Now that I have completed my circuit of the Peloponnesus, which, as I have said, ¹ was the first and the smallest of the peninsulas of which Greece consists, it will be next in order to traverse those that are continuous with it. The second peninsula is the one that adds Megaris to the Peloponnesus, ² so that Crommyon belongs to the Megarians and not to the Corinthians; the third is the one which, in addition to the second, comprises Attica and Boeotia and a part of Phocis and of the Epicnemidian Locrians. I must therefore describe these two. Eudoxus ³ says that if one should imagine a straight line drawn in an easterly direction from the Ceraunian Mountains to Sunium, the promontory of Attica, it would leave on the right, towards the south, the whole of the Peloponnesus, and on the left, towards the north, the continuous coastline from the Ceraunian Mountains to the Crisaean Gulf and Megaris, and the coastline of all Attica. And he believes that the shore which extends from Sunium to the Isthmus would not be so concave as to have a great bend, if to this shore were not added the districts continuous with the Isthmus which form the Hermionic Gulf and Acte; and, in the same way, he believes that the shore which extends from the Ceraunian Mountains to the Corinthian Gulf would not, viewed by itself alone, have so great a bend as to be concave like a gulf if Rhium and Antirrhium did not draw closely together and afford this appearance; and the same is true of the shores ⁴ that surround the recess of the gulf, where the sea in this region ⁵ comes to an end.