According to the traditional account, James Watt one day happened to observe a kettle boiling on the hearth. His aunt, finding him fiddling about (holding a spoon over its spout, removing and replacing it, gauging the pressure, etc) rebuked him for his idleness, suggesting that he go out and do something more productive.

His "idleness" soon led to the development of his famous steam engine.

[According to a similar tale, after trying in vain to solve a particular problem with Thomas Newcomen's design, Watt stopped consciously thinking about it and took a leisurely walk -- whereupon the solution popped into his head.]

["Letters between William Small and Watt were a kaleidoscope of invention and ideas, touching on steam-engines and cylinders; cobalt as a semi-metal; how to boil down copal, the resin of tropical trees, for varnish; lenses and clocks and colours for enamels; alkali and canals; acids and vapours -- as well as the boil on Watt's nose."]