A treadwheel, or treadmill, is a form of engine typically powered by humans. It may resemble a water wheel in appearance, and can be worked either by a human treading paddles set into its circumference (treadmill), or by a human or animal standing inside it (treadwheel). These devices are no longer used for power or punishment, and the term "treadmill" has come to mean an exercise machine for running, walking or other exercises in place.
A horse mill is a mill, sometimes used in conjunction with a watermill or windmill, that uses a horse engine 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, oxen or camels. Treadwheels are engines powered by humans.
A crane is a machine used to move materials both vertically and horizontally, utilizing a system of a boom, hoist, wire ropes or chains, and sheaves for lifting and relocating heavy objects within the swing of its boom. The device uses one or more simple machines, such as the lever and pulley, to create mechanical advantage to do its work. Cranes are commonly employed in transportation for the loading and unloading of freight, in construction for the movement of materials, and in manufacturing for the assembling of heavy equipment.
The first known crane machine was the shaduf, a water-lifting device that was invented in ancient Mesopotamia (modern Iraq) and then appeared in ancient Egyptian technology. Construction cranes later appeared in ancient Greece, where they were powered by men or animals (such as donkeys), and used for the construction of buildings. Larger cranes were later developed in the Roman Empire, employing the use of human treadwheels, permitting the lifting of heavier weights. In the High Middle Ages, harbour cranes were introduced to load and unload ships and assist with their construction—some were built into stone towers for extra strength and stability. The earliest cranes were constructed from wood, but cast iron, iron and steel took over with the coming of the Industrial Revolution.