From prehistoric times levers were used for cultivation, excavation, and moving large objects. Such implements as hoes, slings, and oars were conceived and constructed to enhance human effort. The key to their operation is the relative positions of the load, the pivot called a fulcrum, and the applied effort. To maximize the applied effort, the most effective placement of the fulcrum was found to be close to the load.

As early as 5000 B.C. a simple balance scale employing a lever was used to weigh gold and other items. A Greek device called a steelyard improved on these simple scales by adding a sliding weight to enhance precision. Around 1500 B.C., the shaduf, a forerunner of the crane, made its appearance in Egypt and India as a device for lifting containers of water.

Scholars of this period may well have provided suitable explanations for the mechanics of the...