James Watt

James Watt was a person the First Doctor heavily implied had a hand in developing steam power. He once used Watt as an example of how the most important discoveries could come from the tiniest details. When Ian wondered why the Doctor was so concerned about a mere lost button, the Doctor snapped that he had been with Watt when Watt noticed steam coming out of a kettle. This, the Doctor implied, led to one of Earth's "greatest discoveries". (TV: The Space Museum)