History of the Peloponnesian War

When he could not prevail, neither with the generals nor with the soldiers, having also at last communicated the same to the captains of companies, he gave it over, till at last, the weather not serving to be gone, there came upon the soldiers lying idle a desire, occasioned by dissension, to wall in the place of their own accord.

And falling in hand with the work, they performed it, not with iron tools to hew stone, but picked out such stones as they thought good and afterwards placed them as they would severally fit. And for mortar, where it was needed, for want of vessels they carried it on their backs, with their bodies inclining forward so as it might best lie, and their hands clasped behind to stay it from falling, making all possible haste to prevent the Lacedaemonians and to finish the most assailable parts before they came to succour it.

For the greatest part of the place was strong by nature and needed no fortifying at all.