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

[213] When, therefore, Vespasian looked upon himself as in a manner besieged by these sallies of the Jews, and when his banks were now not far from the walls, he determined to make use of his battering ram. This battering ram is a vast beam of wood like the mast of a ship, its forepart is armed with a thick piece of iron at the head of it, which is so carved as to be like the head of a ram, whence its name is taken. This ram is slung in the air by ropes passing over its middle, and is hung like the balance in a pair of scales from another beam, and braced by strong beams that pass on both sides of it, in the nature of a cross. When this ram is pulled backward by a great number of men with united force, and then thrust forward by the same men, with a mighty noise, it batters the walls with that iron part which is prominent. Nor is there any tower so strong, or walls so broad, that can resist any more than its first batteries, but all are forced to yield to it at last. This was the experiment which the Roman general betook himself to, when he was eagerly bent upon taking the city; but found lying in the field so long to be to his disadvantage, because the Jews would never let him be quiet. So these Romans brought the several engines for galling an enemy nearer to the walls, that they might reach such as were upon the wall, and endeavored to frustrate their attempts; these threw stones and javelins at them; in the like manner did the archers and slingers come both together closer to the wall. This brought matters to such a pass that none of the Jews durst mount the walls, and then it was that the other Romans brought the battering ram that was cased with hurdles all over, and in the tipper part was secured by skins that covered it, and this both for the security of themselves and of the engine. Now, at the very first stroke of this engine, the wall was shaken, and a terrible clamor was raised by the people within the city, as if they were already taken.