I have Kevin Miller to thank for leading me to this wonderful page from one of Isaac Newton’s notebooks. At the same time as he was producing colour by refracting light with glass Newton was also perceiving colour by directly palpating his own eyeball with a wooden bodkin and deforming the wet squishy sphere, thereby putting direct physical pressure on the sensitive interior surface and sending signals which the brain interpreted as light and colour.
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.
Had glass and the newly discovered laws of diffraction written the soul, the spirit and the imagination out of vision, he worried? No, because colour could be produced in vision by something other than the vitreous diffraction of light in either eye or prism. From our point of view his experiment at least established that the body, if not the soul, was deeply implicated in vision. But his notebook drawing of his heroic experiment, which Kevin and I found at a Cambridge University Library online exhibition Footprints of the Lion: Isaac Newton at Work, is wonderful: the tiny hand inserts the bodkin, the sphere is indented like a foot kicking a football in a Harold Edgerton photograph, the concentric circumferences of the origins of the rings of colour are plotted on the retina, but then! — a virtual projection of what he perceived is projected out of the eye into the world. The eye is therefore not only a camera obscura but also a magic lantern! Virtuality, about to stage a comeback with the Oculus Rift is predicted!