|An 18th century artwork entitled “First steam experiment of James Watt”, one of three renditions of the tea kettle anecdote, based on Watt’s cousin Marion Muirhead’s later recollected apocryphal story of how Watt, at age thirteen, became intrigued by the force of steam of a teapot to later go on to “invent the steam engine”. |
The story about a young boy either experimenting with a tea kettle to study the properties of steam or to have gleaned the idea of the steam engine from watching the steam release valve bob up and down, as pointed out by Robert Thurston (1878), is attributed to: Edward Somerset, Thomas Savery, and James Watt. 
Some have reported that Denis Papin envisioned the steam engine by watching the pressure release valve bob up and down on his pressure cooker (see: Papin digester).
In c.1829, Francois Arago was reporting the story in respect to James Watt. 
1. Thurston, Robert. (1878). A History of the Growth of the Steam-Engine (txt) (pg. 81). Appleton and Company.
2. Marsden, Ben. (2002). Watt’s Perfect Engine: Steam and the Age of Invention (pgs. 10-11) (image). Icon.