Here some original texts which I think are too hard to find:

Robert Grosseteste
“De Luce” (“On Light” or “The Beginning of Forms”)

Written in the first half of the thirteenth century, this is one of the main sources of the medieval metaphysics of light. This text was also a very important influence on later writers on ‘perspectiva’, such as Roger Bacon and John Pecham.
Particularly interesting I find the link between mathematics and light Grosseteste develops, since he considers light to be something we would now perhaps call ‘extension’, so that light in fact determines the structure of space.

Peter Mark Roget
“Explanation of an Optical Deception in the Appearance of the Spokes of a Wheel seen through Vertical Apertures“
Philosophical Transactions of the Royal Society, London, 1825.

Text in which a curious interference phenomenon is explained by supposing it to be caused by a trace on the retina, built up over time. One of the seminal texts in the activity that led to the invention of optical toys such as the phenakistiscope and, eventually, cinema.

Alexander Wallace Rimington
“A New Art: Colour-Music“
A paper read at St. James’s Hall on June 6, 1895,
reprinted in ‘Colour Music, the Art of Light’, by A.B.Klein, Lockwood, London, 1930, pp 256-261.

A pamphlet describing the main goals and inspirations Rimington had when he developed his colour-organ. This text accompanied his first public presentation of the new art he thought to have invented, and it is a good summary of his later book ‘Colour-Music, the Art of Mobile Colour’ (Hutchinson, London, 1912).
In developing his colour-organ, Rimington started from the close analogy he perceived between colour and musical pitch. The organ he built was designed to make it possible to play conventional musical scores, which would then be translated into colour sequences. He did not see this translation as the main goal of his invention, but saw it as a rather primitive starting point from which he could see a new autonomous art unfolding. A very interesting question raised by Rimington’s approach is that of tempo: his performances must have been decidedly stroboscopic, even to our post-mtv standards, since every single musical note is translated into a colour-change. Another not unrelated question is that of the necessity to educate the eyes of a public unaccustomed to these new colour sensations.

W. Grey Walter
“The Design of M. Speculatrix“

A text written by W. Grey Walter and published as an appendix to his book “The Living Brain”, Duckworth, 1953.
It describes in some detail the construction of his Machina Speculatrix, a species of mobile autonomous robot of which he built two individuals around 1948, called Elmer and Elsie.
Only the ‘Fig. 19’ circuit diagram originally belongs to this text, the others come from various sources. Note the images of Elsie looking into the mirror !

William Katavolos
“Organics“

A great, dreamy text from 1961 to which I have seen quite a few references but which is pretty hard to find. As far as I know William Katavolos has never been a ‘standard’ architect and as far as I know this text is the only one he ever published on the subject. In his book ‘Nanoarchitecture’ John Johansen refers to him as a physicist and credits him as being the first to sow the notion of a ‘growing architecture’. In light of the current developments in nanotechnology, artificial life, modular robotics and interactive architecture, the dreamy ideas of Katavolos appear suddenly again very relevant.