Medieval episodes of portaging the Corinthian Isthmus are unsurprisingly scant. The only account cited with any frequency is the remarkable portage of Niketas Ooryphas’ in AD 872. The portage is disputed, but the historical records for the account are certain.
Two other supposed medieval portages turn out to be dead ends. In an article titled “Railways in the Greek and Roman World,” M.J.T. Lewis notes (p. 12) that the 12th century Moroccan geographer Al Idrisi refers to the transfer of small ships over the Corinthian Isthmus (see p. p. 123 of this volume). Indeed, he does, but the account is a derivative summary of Strabo 8.2.1, not first-hand observation. In a similar way, Apostolos Papaphotiou, who notes the Al Idrisi account in his book on the diolkos, also records a text about a man who traveled by boat from Venice to Corinth and from there to Armiro (which Papaphotiou places in Thessaly), where he takes another boat to Constantinople. Papaphotiou reads this as evidence for transfer of ships over the isthmus, but the text doesn’t actually say that, and we should not and cannot rule out a circumnavigation.
So, no unambiguous accounts for the Medieval or Ottoman era. That is, until I stumbled upon one as I was was reading some early travel accounts to the Corinthia. On page 240-241 of his Travels in Greece (1776), Richard Chandler gives us an interesting reference to ship portaging:
“The root of mount Oneius extending along the lsthmus rendered the Corinthian territory which was not rich in soil browy and uneven with hollows. On the side of the Corinthian gulf the beach receded toward that of Schoenus which was opposite. There the neck was most narrow, the interval between the two seas being only forty stadia or five miles; and there was the Diolcos or drawing-place, at which it was usual to convey light vessels across on machines. The same practice prevailed in the wars of the Turks and Venetians.”
Which of the wars were opportunities for ship portaging is unclear from the passage, but Chandler clearly believed for some reason that it occurred. I have not yet found an earlier source that refers to this, although it perhaps is still out there waiting to be discovered. That Chandler mentions it so casually in passing reminds me a bit of how scholars have frequently read Strabo’s casual reference to ship portaging—but here, Chandler clearly places portaging in some murky time frame. Nakas and Koutsoumba have noted better-documented accounts of Venetian portages in their forthcoming piece on the diolkos, so there’s no reason at least to dismiss Chandler’s account out of hand. Of course, it may be that Chandler was thinking about these other accounts as he visited the Isthmus.
When I floated the question about this portage to the Medieval and Post-Medieval Archaeology FB group, Diana Wright remarkably dug up a letter referring to the dragging of cannon between Corinth and Kenchreai in May 1480! So far as I know, that is the only account preserving the dragging of anything between Corinth and its eastern harbor.
So, I’ll add these to the list, and update the diolkos page, and scratch my head about Chandler’s reference, until someone clarifies it all for me or I stumble by accident on another forgotten document.