Set of two small instruments of similar design: the first is a heavy square with a magnetic compass (missing its magnetic needle) with mobile indexes and two graduated circles; the second is a triangle, bearing on its side the initials of its maker, "C. T." (Christoph Trechsler), and a small arc with decreasing graduations that represent a linear scale. Brought to Florence from Germany by Prince Mattias de' Medici in the first half of the seventeenth century.