1. The diary of Benjamin Robert Haydon, ed. by Pope W. B. (5 vols, Cambridge, MA, 1960–63), ii, 173.
2. Artists' Colors and Newton's Colors
3. Newton Isaac, Opticks, based on the fourth edition London, 1730 (New York, 1952), Bk I, Pt II, Prop. III, Problem I, 126, my emphasis. The ellipses indicate where I have omitted Newton's labelling of the lines in accordance with his accompanying diagram.