In 1919 the engineer-gemologist Marcel Tolkowsky published *Diamond Design*, deriving the round brilliant cut from first principles of optics — crown and pavilion angles tuned to trap and return light. His plates were thin black line-work on white: crown sections, pavilion sections, refraction and total-internal-reflection ray paths, dotted construction normals.

This system reissues that engineering drawing as a blueprint. The diagram inverts to luminous cyan strokes on a dark teal-blue field — all line, no fill — where 34.5° and 40.75° callouts, 58-facet geometry, and dimension figures read like a cyanotype technical print rather than a sparkling photographic render.