Optical properties and theory of color of pigments and paints
A 1917 technical monograph on pigment colour, published by the American Society for Testing Materials and written by H. E. Merwin for analysts and paint chemists. Its two pictures are scientific diagrams: a triangular colour chart with labelled corners and grid lines, and a second triangle with curved trajectories linking named pigments such as verdigris, vermilion and Prussian blue. A designer might take from them the idea of mapping colour mixtures as lines and fields on a triangle.
