History of the Peloponnesian War

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.