Card divination has long been a particularly iconic aspect of the Portuguese Book of Saint Cyprian, featuring in the cover illustrations of most of its nineteenth-century versions. Included in many of the cartomancy incantations is a small pseudo-hagiographical narrative which mentions a supposed seven-year seafaring journey made by Saint Cyprian himself. The origin and meaning of these thematically coherent incantations, as related to these cartomancy systems (or any other 'Cyprianic' divination method), has until now remained unresolved.

In Clearing the Waters: A Monograph on Saint Cyprian Divination from the 17th to the 19th Century, author José Leitão utilises Portuguese Inquisition records and Prosecutor's Notebooks to unravel the mystery of the seafaring incantation, and how it has come to be associated with contemporary Cyprian divination. Also included is a discussion of other divinatory techniques found in the Book of Saint Cyprian, such as coscinomancy, favomancy, and hydromancy, of which many examples can be found in the extensive appendices.