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

[44] In short, if any one will suppose that Galilee is inferior to Perea in magnitude, he will be obliged to prefer it before it in its strength; for this is all capable of cultivation, and is every where fruitful; but for Perea, which is indeed much larger in extent, the greater part of it is desert and rough, and much less disposed for the production of the milder kinds of fruits; yet hath it a moist soil [in other parts], and produces all kinds of fruits, and its plains are planted with trees of all sorts, while yet the olive tree, the vine, and the palm tree are chiefly cultivated there. It is also sufficiently watered with torrents, which issue out of the mountains, and with springs that never fail to run, even when the torrents fail them, as they do in the dog-days. Now the length of Perea is from Macherus to Pella, and its breadth from Philadelphia to Jordan; its northern parts are bounded by Pella, as we have already said, as well as its Western with Jordan; the land of Moab is its southern border, and its eastern limits reach to Arabia, and Silbonitis, and besides to Philadelphene and Gerasa.