History of the Peloponnesian War
Thucydides
Thucydides. History of the Peloponnesian War. Crawley, Richard, translator. London and Toronto: J. M. Dent and Sons Ltd.; New York: E. P. Dutton and Co., 1914.
The length required for the ladders was thus obtained, being calculated from the breadth of the brick.
Now the wall of the Peloponnesians was constructed as follows. It consisted of two lines drawn round the place, one against the Plataeans, the other against any attack on the outside from Athens, about sixteen feet apart.