" It consists of a tank built from heavy sheet iron in which I store air under a pressure of fifty atmospheres. This tank is fastened to the back by means of straps, like a soldier’s knapsack. Its top part forms a box where the air is regulated by a bellows mechanism and can be released only at its proper tension. In the Rouquayrol device that has been in general use, two india-rubber hoses leave this box and feed to a kind of tent that imprisons the operator’s "

― Jules Verne , Jules Verne Collection, 33 Works: A Journey to the Center of the Earth, Twenty Thousand Leagues Under the Sea, Around the World in Eighty Days, The Mysterious Island, PLUS MORE!