William Blake (1757-1827) created his Newton as an 18″x24″ color print finished in pen and ink and watercolor around 1805. It works just nicely on the cover of the Universe Symphony. However Blake was actually taking issue with Isaac Newton, satirising him and implying that even if he could measure everything he still would not know all the secrets of the universe. Blake, a religious and mystical man, shows Newton with his dividers measuring the symbol of the Trinity, which he implied is not measurable.

See another Blake image that was a cover candidate before we settled on Newton.

Thanks for background especially to the William Blake exhibition at the Tate, London, 2000/1, the catalog of which is one of the best illustrated books about the artist. The museum also has an extensive online Blake section relating to that exhibition.
William Blake, ISBN 0-8109-5710-8 (Abrams)

Download a bundle of four five-minute excerpts from the Universe Symphony (18Mb): mp3 | m4a