The apparatus combines the effects of three class 1 levers. The levers, mounted on three lathe-turned columns on sliding supports, have lead counterweights which serve to balance them in the absence of applied force. The combined action of the three levers makes it possible to balance one weight with another that is much smaller than would be needed with a single lever.

Since the late 18^th century, devices featuring class 1, 2 and 3 levers, together with pulleys and inclined planes, have constituted the basic equipment of physics cabinets for demonstrating the laws of mechanics.
This particular instrument is listed in the first inventory of the Collegio Mariano Physics Cabinet, dated 1793.
Device on display.