Theodolite with wooden support, consisting of a circular plane fitted onto a straight base. The plane carries a round sheet of paper with the compass and a diopter at its center. At the center of the straight base is hinged another diopter bearing a vertical semi-circle with a degree scale and plumb bob. In surveying work, the position angles of the points sighted would be marked on the sheet. Distances and heights were computed by reading the angle of inclination of the line of sight shown by the plumb bob on the vertical semi-circle. For building surveys, the straight base could be held against the wall to determine the wall's orientation relative to the magnetic north. Provenance: Medici collections.