From: The Virginia Medical Journal, Volume 2, 1875, Page 685. “The principal parts of Waldenburg’s apparatus are two spirometer-like sheet zinc cylinders, fitting one into the other – the outer one meter high and 30 cm in diameter. The outer one is filled to a mark with water, as in the spirometer. The cover of the inner cylinder has an opening for a manometer, and one for a flexible tube leading to an ori-nasal mask. If the inner cylinder, resting on the bottom of the outer cylinder, with the stopcock closed is raised and and held by weight, the contained air is rarified; if this cylinder receives air at atmospheric pressure, and the stopcock is then closed, the cylinder being made to descend by weights, the air is condensed. According to the capacity of the lungs, 5-30 inhalations empty a fully charged apparatus.”