Nowadays, pop-up books and flap books are mostly found in the children's section, but centuries ago, they served a much more educational purpose. As early as the 16th century, paper flaps were integrated into anatomy books to illustrate how the parts of the body all fit together and overlap.
They are things of deeply intricate beauty and craft, but also highly delicate and rare. The average person will never get a chance to handle one in person, but, thanks to the wonders of digitisation, we can pore over the pages at leisure.
"Kleiner welt spiegel, das ist, abbildung göttlicher schöpffung an dess menschen leib : mit beygesetzer schrifftlicher Erklärung : so wo zu Gottes Weissheit : als dess menschen selbst erkandtnuss dienend" is the somewhat tongue-twisting title of a volume recently digitised by the Archives & Special Collections at Columbia University's Augustus C. Long Health Sciences Library.
Published in 1661, the volume is a German translation of an earlier work, the more concisely titled "Catoptrum Microcosmicum," written in Latin by Johann Remmelin and published in 1613. It was intended more as an informative tome for curious-minded laypeople than a textbook for the medical professional. And it appeared that people were curious indeed, as the book became a bestseller.
Getting the delicate book fit for digitisation was a tricky prospect. Many of the flaps had become tangled, and needed to be carefully flattened and mended so that they wouldn't tear. Also, the book had been stained, which obscured the text and made the pages brittle. This was painstakingly lightened using moisture and a suction device. Finally, the book was rebound.
The book was then imaged with every flap folded and unfolded. There is only one page that includes flaps, showing bodies of a man and a woman, the torso of a pregnant woman between them. Multiple flaps lift to show nerves, veins, muscles, and bones.
In all, the page contains over 120 flaps. These had to be lifted using fine brushes and spatulas to avoid damage, with pieces of glass placed between them to make the flaps appear as though they are standing. Lifting each flap and placing the glass required the work of as many as four librarians. Then a glass was placed between the book and the camera, and the page was photographed.
The digitised book has been uploaded to Archive.org, where you can download it in a variety of file formats in high resolution.