Quadrant, by D Lusuerg of Rome, 1701.

This instrument is part of a set that would have been made to order for a wealthy client and regarded more as an adornment and status symbol than as practical tools for practitioners. The quadrant is an instrument carrying a quarter-circle arc which, in its earliest form, was used by astronomers to find the altitudes of stars and planets. The surveyor's quadrant developed as a much smaller and more portable form and was used to measure the altitude of terrestrial objects.