Astronomical Instruments of the Imperial Observatory

A detailed woodcut of a sector or proportional compass resting on a tessellated floor. The two hinged legs feature scales labeled with Chinese numerals 1 through 9 and 100, while the connecting arc contains scales marked 10 through 13. The hinge is marked 'Wu'. To the right, a support frame is marked 'Ru'. The floor grid includes the character 'Bai' (hundred).