The apparatus shows the combined effect of three first-order levers. The levers, mounted on four turned columns, each carry a brass counterweight to maintain their equilibrium when no effort is applied to them. Brass strips and equidistant nails on the levers show possible application points for loads and efforts. The design is based on a model illustrated by Willem Jacob 's Gravesande in Physices elementa mathematica, experimentis confirmata (3rd ed., Leiden, 1742). Provenance: Lorraine collections.