Illustration of a man using a circumferentor, or surveyor's compass, a forerunner of the theodolite (a more sophisticated sextant that can measure both a horizontal and a vertical angle through a full 360簞), from an illustrated book on cosmography by Jacques de Vaulx (or Devaulx), a pilot of Le Havre, called, "Les Premi矇res Euvres de Jacques de Vaulx, pillote en la Marine," 1583.