The Romans who farmed and grew food in Italy relied on at least three different methods to grind their grains into more palatable meal and flour. Virtuous early Republicans used hand querns, which maintained their popularity throughout Roman history on account of their simplicity for users. Larger mills also existed. Their round stones could be housed in special buildings, where they moved in circular fashion, pushed by animals (especially donkeys) or slaves and other subalterns. “Fed” grain from an opening in the center of the uppermost stone, such “sweat” mills poured meal out below. In this they differed little from hydraulic mills, whose stones, however, revolved thanks to flowing water.

None of the various grinding methods in Roman Italy superseded the others, even though they may have been chronological successors of one another. Several methods instead coexisted harmoniously, for each had much to recommend it and each had a social, economic, and ecological niche in the Roman Mediterranean. While a peasant in a remote, water-less plateau might find a hand quern the best system for grinding his grain, in the foothills of the Alps, where water gushed strong and reliable, the allure of hydraulic power would be irresistible. In Rome itself, where hundreds of thousands of mouths clamored for bread, the efficiencies of mechanization were obvious. The annona used both “sweat” and water mills in the city, as complementary techniques for milling. Thus, in Procopius' finely told tale of a Gothic siege of Rome in 537, a flour shortage threatened the city only when the aqueducts had been cut (no water power was available) and there was no fodder for animals (the main source of “sweat” power).