 German Jesuit scientist Gaspar Schott heard from a traveler about a small camera obscura device he had seen in Spain, which one could carry under one arm and could be hidden under a coat.He then constructed his own sliding box camera obscura, which could focus by sliding a wooden box part fitted inside another wooden box part.He wrote about this in his 1657 "Magia universalis naturæ et artis" (volume 1 – book 4 "Magia Optica" pages 199–201).