Nicht-Euklidische Geometrie
Felix Klein's German lecture notes on non-Euclidean geometry, issued at Göttingen in 1893 for university mathematics students following his course. The 45 plates are hand-drawn pen diagrams — cones tangent to spheres, conics crossed by tangent lines, spherical triangles with hatched faces — with dashed hidden edges, numbered scales, and cursive "Fig." captions on toned paper, useful for loose geometric line work and handwritten labelling.
