Surveying compass composed of two flat legs, one of which ends in a screw for fastening the instrument to a support. The legs have four mobile sights and two cursors fitted with long tips at right angles to each other. The legs carry a 190-part graduation on the front and several arithmetical scales on the back. In addition to measuring position angles in surveying work, the instrument could be used as a set of proportional compasses. Provenance: Vincenzo Viviani bequest.