Manuscript lesson of the day: anti-theft edition! Here's an inventory of books from St Paul's Cathedral Library, written up in 1458. It is written in the form of a chirograph, with wavy lines at the edge. Explanation in the next tweets. (BL Cotton Charter xiii.2) /1

Two identical copies were drawn up then cut along the line at the left, each held by a different individual. At a given time, a chaplain would be asked to show this inventory next to its copy for a shelf audit. /2

This helped identify books missing from the shelves. The wavy lines ensure that the copies brought together were those written at the same time & are exact copies. This prevented the chaplain from forging a copy of the inventory which might leave off any books he had stolen. /3

Medieval manuscripts have lots of different anti-theft and authentication devices, and these aren't limited to the modern age. One of my favorites is an anti-forgery technique that I've seen used by legal scribes in medieval Spain. Will see if I can find a photo... /4

Not a vibrant example & it's from the 16C. But anyway: in order to ensure that no one would come along & add text to a legal document, scribes in Spain wd scribble lines or hatching above & below the text, just like I do when I write in the amount on a check today. /5

I got that photo from the above tweet here: https://en.todocoleccion.net/antique-manuscripts/carta-ejecutoria-hidalguia-hernando-naveda-vecino-belorado-burgos-ano-1541-pergamino~x108800884#sobre_el_lote

I've seen examples with WAY more hatching above and below the text. /6