Modern heliographic processes : a manual of instruction in the art of reproducing drawings, engravings, manuscripts, etc., by the action of light : for the use of engineers, architects, draughtsmen, artists, and scientists (1888)
Lietze, Ernst · New York : Van Nostrand · leaf 9
Ordinary Blue Print.— Negative. … Ordinary Blue Print.— Positive.
Photographic reproduction of plans, drawings, etc · Photography
Internet Archive · Getty Research Institute · Public domain (published before 1931). Free to use for anything.
