Monks, manuscripts and sundials : the navicula in medieval England /by Catherine Eagleton.

"The navicula sundial, because of its rarity and attractive form, has interested curators and historians alike. Although apparently a specifically English instrument, there is much debate about when and where it was invented, and about who made and used the five surviving medieval examples. This book brings together for the first time evidence from the surviving instruments, and written sources including four previously unknown texts describing how to make or use the instrument."--Back cover.