A sundial consists of a gnomon, which casts the Sun’s shadow, and a dial on which the shadow indicates the time. This simple portable sundial features a gnomon that can be adjusted according to one’s latitude. Sundials have ranged in size from pocket-dials to monumental architecture.

Nocturnal dials tell time by the stars. This instrument replicates an original nocturnal dial created by Girolano della Volpaia in Florence in 1569, held in the Museo Galileo in Florence.

The astrolabe, one of the fundamental instruments for observational astronomy, consists of three major parts: the mater, the underlying disk; the climate, a removable disk adjusted for latitude; and the rete, a ring marked with star positions.

The abacus, an ancient calculating machine, is still in use around the world. Counters consisting of pebbles in the sand, beads on a wire or knots on a string are shifted back and forth on each level to represent different quantities, such as units and tens.

This book explains how to use the terrestrial and celestial globes, an armillary sphere (which shows the movements of the sky), and an orrery (which models the motions of the planets). Martin operated an instrument shop in London.