for
These devices operate on the straightforward principle that atmospheric pressure varies inversely with elevation.
Its use in practice (Determination of Altitude with the Aneroid Barometer, Iowa Academy of Science, 1953): https://scholarworks.uni.edu/cgi/viewcontent.cgi?article=3169&context=pias
A similar unit at the Smithsonian: https://americanhistory.si.edu/collections/search/object/nmah_1420464
