David Ramsay Hay’s mapping of colour onto musical notes, a diagram from his The Laws of Harmonious Colouring (1838).⠀More in @carmelrazmusic's essay “Music of the Squares” on a Hay's attempt to use music theory to evaluate visual beauty — https://publicdomainreview.org/essay/music-of-the-squares-david-ramsay-hay-and-the-reinvention-of-pythagorean-aesthetics