41.5 x 16.2 x 23 Wood, brass, steel, silver and leather
Spherical magnet mounted on a stand
41.5 x 16.2 x 23 Wood, brass, steel, silver and leather
Dalla Bella, Giovanvanni Antonio, Physices Elementa, Coimbra, 1790, Vol. III, Pl. VI, Fig. 22.