Triangulation Instrument

This instrument is a form of surveying device. Its inscription says it is used "to find the distance by means of the surface." By taking angular measurements to a distant point from two locations and using the known distance between the two measuring points, the surveyor could use simple geometry to figure out how faraway the point was. Constructed in the 16th century, it consists of a finely graduated 125 degree circular sector and two rulers each divided into 44 parts.