"During the middle ages wax tablets were in general use. Daily life cannot be imagined without them: students were supposed to carry a diptych at their belt for easy use, while writers used them for rough notes. They were also employed in private correspondence. Above all, medieval accounts were kept to a large extent on wax tablets, and most of the surviving examples served this purpose; even books of wax tablets were formed. In some places the use of wax tablets for accounting continued up to the nineteenth century" (Bernhard Bischoff, Latin Palaeography. Antiquity & the Middle Ages  14).