To this end the merciful angels often proposed and invented figures, characters, forms and unknown words from us mortals, and wonderful and meaningless according to the usual practices of the language, but inducing us through the highest admiration our reason, a diligent search of intelligible things, then the veneration and love of these things.
Johannes Reuchlin, De Arte Cabalistica, Hagenhau
Cyanotype is a photographic printing process that produces a cyan-blue print. Engineers used the process well into the 20th century as a simple and low-cost process to produce copies of drawings, referred to as blueprints. The process uses two chemicals: ammonium iron(III) citrate and potassium ferricyanide.