Gesammelte Abhandlungen über physiologische Optik
Collected papers on physiological optics by the German physician August Classen, published in Berlin by Hirschwald in 1868 for physiologists and eye doctors. The plates are spare letterpress line diagrams: paired circles marked L and R for the two eyes, straight and dashed sight lines converging on lettered points along a horizontal axis, and a ruled rectangle crossed by axes with a single arc — usable as geometric schematics, arrow-free ray fans, and annotated grid frames.
