On Architecture

2. Afterwards a carpenter from Tyre, Bright by name and by nature, was led by this invention into setting up a mast from which he hung another crosswise like a steelyard, and so, by swinging it vigorously to and fro, he threw down the wall of Cadiz. Geras of Chalcedon was the first to make a wooden platform with wheels under it, upon which he constructed a framework of uprights and crosspieces, and within it he hung the ram, and covered it with oxhide for the better protection of the men who were stationed in the machine to batter the wall. As the machine made but slow progress, he first gave it the name of the tortoise of the ram.

3. These were the first steps then taken towards that kind of machinery, but afterwards, when Philip, the son of Amyntas, was besieging Byzantium, it was developed in many varieties and made handier by Polyidus the Thessalian. His pupils were Diades and Charias, who served with Alexander. Diades shows in his writings that he invented moveable towers, which he used also to take apart and carry round with the army, and likewise the borer, and the scaling machine, by means of which one can cross over to the wall on a level with the top of it, as well as the destroyer called the raven, or by others the crane.