Flavius Josephus, The Wars of the Jews
William Whiston, A.M., Ed.

[275] For now it was that the Roman general came, and led his army against Eleazar and those Sicarii who held the fortress Masada together with him; and for the whole country adjoining, he presently gained it, and put garrisons into the most proper places of it; he also built a wall quite round the entire fortress, that none of the besieged might easily escape; he also set his men to guard the several parts of it; he also pitched his camp in such an agreeable place as he had chosen for the siege, and at which place the rock belonging to the fortress did make the nearest approach to the neighboring mountain, which yet was a place of difficulty for getting plenty of provisions; for it was not only food that was to be brought from a great distance [to the army], and this with a great deal of pain to those Jews who were appointed for that purpose, but water was also to be brought to the camp, because the place afforded no fountain that was near it. When therefore Silva had ordered these affairs beforehand, he fell to besieging the place; which siege was likely to stand in need of a great deal of skill and pains, by reason of the strength of the fortress, the nature of which I will now describe.