This section opens with a manuscript with a peculiar shape and format. Like most objects, books are confined to the space they occupy, obedient as they are to the laws of nature. That is to say, unlike the Incredible Hulk, they do not expand beyond the limits of their own physicality. This chapter will challenge your beliefs if you agree with this. It draws attention to a manuscript type that does expand: with a flick of the finger or a gesture of the hand the dimensions of these special objects increase dramatically, up to ten times their original size—or more. As if defying the laws of nature, this miraculous expansion increased the available writing space in objects that were principally designed to be small and portable. What do these objects look like? And what was the drive behind their production?

Bat Books

Produced in England in ca. 1415– 1420, the small manuscript in Figure 82 contains a calendar as well as astrological tables and diagrams. The information was used by physicians to diagnose and prognosticate, while the calendar provided information about religious feasts. The Leiden codicologist Peter Gumbert (d. 2016) coined the term “bat book” for this type of manuscript, alluding to its expanding nature: the book stretched its wings, as it were, when used. Moreover, in an unused state the book would be hanging from the owner's belt in an upside down orientation, like a bat. Gumbert's inventory holds sixty-three items, and many of them look more scruffy than the handsome specimen in the Wellcome Library. Folding almanacs were especially popular in late-medieval England, if the surviving specimens form an accurate representation.

These bookish objects are especially interesting from a material point of view. During production, folding almanacs looked very much like a regular book: the scribe filled regular pages with text. However, in a completed state, when the binding was added, the pages were folded in a very clever way, giving them an “unbookish” look. The two different states (a small package when closed, irregular dimensions when unfolded) were chosen with care: closed, it was a portable book that could dangle from the owner's belt, while in its extended state the reader was provided with expansive information at a glance.