A
horse mill is a mill, sometimes used in conjunction with a
watermill or
windmill, that uses a
horse as the power source. Any milling process can be powered in this way, but the most frequent use of animal power in horse mills was for
grinding grain and pumping water. Other
animal engines for powering mills are powered by
dogs,
donkeys and
oxen.
Treadwheels are engines powered by humans.