The De ingeneiis examines themes of civil and military engineering, with a special focus on hydraulics, a subject of crucial importance to the city of Siena at whose service Taccola worked at length. He himself chose his nickname "Archimedes of Siena." A great expert on the Ancients and aided by drawings, Taccola addressed problems of primary importance for the times, reducing the mechanical apparatus to combinations of the levers, pulleys and gears first seen in Antiquity.