Notes from Johannes Kepler and Isaac Newton

Johannes KeplerKopie eines verlorengegangenen Originals von 1610
Portrait of Johannes Kepler (1571-1630) by unknown artist, 1610.
Plate from Astronomiae Pars Optica (1604) by Kepler illustrating eye anatomy.
Portrait of Isaac Newton (1642-1726) by Godfrey Kneller, 1689.
Page from Newton’s personal journal indicating experiments he did on his own eye: “I tooke a bodkine gh & put it betwixt my eye & [the] bone as neare to [the] backside of my eye as I could: & pressing my eye [with the] end of it (soe as to make [the] curvature a, bcdef in my eye) there appeared severall white darke & coloured circles r, s, t, &c. Which circles were plainest when I continued to rub my eye [with the] point of [the] bodkine, but if I held my eye & [the] bodkin still, though I continued to presse my eye [with] it yet [the] circles would grow faint & often disappeare untill I removed [them] by moving my eye or [the] bodkin. If [the] experiment were done in a light roome so [that] though my eyes were shut some light would get through their lidds There appeared a greate broade blewish darke circle outmost (as ts), & [within] that another light spot srs whose colour was much like [that] in [the] rest of [the] eye as at k. Within [which] spot appeared still another blew spot r espetially if I pressed my eye hard & [with] a small pointed bodkin. & outmost at vt appeared a verge of light.”
Page from original manuscript of Newton’s Philosophia Naturalis Principia Mathematica (1687). Image from Cambridge University Library.