A man using a cros-staff to measure angles, 1535.
© Science Museum / Science & Society Picture Library
Hand-coloured woodcut from the 'Book of Geometry', part of the 'Margarita Philosophica' by Gregor Reisch (c 1467-1525). The Medieval Jewish scholar Levi ben Gersohn first used the cros-staff as an astronomical tool in 1342. Aided by an asistant, Gersohn operated a long staff to move the cros-piece, thus enabling him to measure a broad range of angles. First printed in 1503, the 'Margarita Philosophica' was an encyclopaedic text book for scholars divided into twelve 'books', each dealing with the science of one of the following: grammar, dialectics, rhetoric, arithmetic, music, geometry, astronomy, natural philosophy (physics), origin of natural objects (natural history), psychology, logic and ethics.