Josephus reports that once the Romans had completed their great siege ramp on the west side of Masada, they brought up an enormous tower on wheels, over one hundred feet high (based on a twenty-inch cubit) and entirely encased in iron. From this tower, Roman artillery opened fire on those defending the walls, sending showers of stones and other missiles down on them and forcing them to retreat into the fortress. With this objective accomplished, a great battering ram began the assault on the walls, and the fall of Masada became imminent.
Nineteen hundred years later, the excavation team led by Yigael Yadin found strewn all about Masada the remains of this episode: hundreds of rounded stones of the sort fired from Roman artillery. The excavation reports indicate that these stones were found in most areas of the fortress. Many were piled in the rooms along the casemate wall and were "of the size of oranges and grapefruits."
These stones are typical of projectiles thrown by various Roman ballistae, catapults, and "artillery machines." Indeed, Josephus speaks of "numerous quick-firers and ballistae." "Quick-firers" refers to the scorpio, or the manuballista, a small, quick-firing catapult that shot thin arrows and could be loaded and fired by just one man. The stones found at Masada belonged to the ballista, a very versatile and powerful artillery piece that resembled a large crossbow rather than the conventional one-armed catapult. The versatility came from its ability to fire a wide range of stones and to be aimed with great precision even at high angles, such as those required to bombard fortress walls. This capability, coupled with the powerful force with which it fired stones, made the ballista a dreaded machine.