Third-order lever inspired by a model proposed by Willem Jacob 's Gravesande in Physices elementa mathematica, experimentis confirmata (3rd ed., Leiden, 1742). There is a beam with two notches and three evenly spaced nails showing the points where the effort could be applied. The effort consists of a pan connected to the beam by a cord passing on a pulley. A second pan hanging from one end of the beam represents the load. Provenance: Lorraine collections.