History of the Peloponnesian War
Thucydides
Thucydides, Vol. 1-4. Smith, Charles Foster, translator. London and Cambridge, MA: Heinemann and Harvard University Press, 1919-1923.
furthermore, the device of the grappling-irons had already been reported to them, and while they were equipping their ships to meet every other contingency, they also took precautions against this. For they stretched hides over the prows and a considerable portion of the upper works of the ships, in order that when the grapnel was thrown it might slip off and not get hold.
And when all was ready, Gylippus and his generals exhorted their men as follows:
"That the deeds which have already been achieved are glorious and that the contest will be for glories still to come, you, Syracusans and allies, seem to us most of you to be aware—otherwise you would not have laid your hands to the task so zealously; but if anyone has not perceived this as clearly as he should, we will make it plain.