History of the Peloponnesian War

At first all were to take part, but afterwards half of them somehow lost heart, thinking the risk too great, and only about two hundred and twenty voluntarily persisted in making the sortie, which was carried out in the following way.

They made ladders equal in height to the enemy's wall, getting the measure by counting the layers of bricks at a point where the enemy's wall on the side facing Plataea happened not to have been plastered over. Many counted the layers at the same time, and while some were sure to make a mistake, the majority were likely to hit the true count, especially since they counted time and again, and, besides, were at no great distance, and the part of the wall they wished to see was easily visible.

The measurement of the ladders, then, they got at in this way, reckoning the measure from the thickness of the bricks.

The wall of the Peloponnesians was built in the following fashion. It had two encircling lines, the inner looking towards Plataea, the outer to guard against attack from the direction of Athens, and the two circuits were distant about sixteen feet from one another.