When once the idea of the separate condensation was started, all these improvements followed as corollaries in quick succession, so that in the course of one or two days the invention was thus far complete in my mind, and I immediately set about an experiment to verify it practically.

As quoted in "Notes on Professor Robison's Dissertation on Steam-engines" (1769) from Robison's Essays on Various Subjects of Mechanical Philosophy (1822) ed. David Brewster Vol. 2, p. 347