History of the Peloponnesian War

The same winter the Plataeans (for they were besieged by the Peloponnesians and Boeotians), pressed now with want of victual and hopeless of relief from Athens, and no other means of safety appearing, took counsel, both they and the Athenians that were besieged with them, at first all to go out and, if they could, to pass over the wall of the enemy by force. The authors of this attempt, were Theaenetus the son of Tolmidas, a soothsayer, and Eupompidas the son of Daimachus, one of their commanders.

But half of them afterwards, by one means or other, for the greatness of the danger shrunk from it again; but two hundred and twenty or thereabouts voluntarily persisted to go out in this manner.

They made them ladders fit for the height of the enemy's wall; the wall they measured by the lays of bricks on the part toward the town where it was not plastered over; and divers men at once numbered the lays of bricks, whereof, though some missed, yet the greatest part took the reckoning just, especially numbering them so often and at no great distance but where they might easily see the part to which their ladders were to be applied, and so by guess of the thickness of one brick took the measure of their ladders.