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.

As for the wall of the Peloponnesians, it was thus built. It consisted of a double circle, one towards Plataea and another outward in case of an assault from Athens. These two walls were distant one from the other about sixteen foot;

and that sixteen foot of space which was betwixt them was disposed and built into cabins for the watchmen, which was so joined and continued one to another that the whole appeared to be one thick wall with battlements on either side.

At every ten battlements stood a great tower of a just breadth to comprehend both walls and reach from the outmost to the inmost front of the whole, so that there was no passage by the side of a tower but through the midst of it.

And such nights as there happened any storm of rain, they used to quit the battlements of the wall and to watch under the towers, as being not far asunder and covered beside overhead. Such was the form of the wall wherein the Peloponnesians kept their watch.