... that it would be possible to make a machine light enough and powerful enough to raise itself without the agency of a balloon. From the first I was convinced that it would be quite out of the question to employ a balloon in any form. At that time the light high-speed petrol motor had no existence. The only power available being steam-engines, I made all my calculations with a view of using steam as the motive power. While I was studying the question of the possibility of making a flying machine that would actually fly, I became convinced ... — The Mastery of the Air • William J. Claxton
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