Italian polymath Giambattista della Porta described the camera obscura, which he called "obscurum cubiculum", in the 1558 first edition of his book series "Magia Naturalis". He suggested to use a convex mirror to project the image onto paper and to use this as a drawing aid. Della Porta compared the human eye to the camera obscura: "For the image is let into the eye through the eyeball just as here through the window". The popularity of Della Porta's books helped spread knowledge of the camera obscura.