The antiquarian work of the French orientalist Emile Prisse d'Avennes in Egypt has been mainly analysed through his notorious illustrated publications that have been continuously reprinted, in many languages, since their release in the 1870s. His private papers kept at the Bibliothèque nationale de France in Paris, as well as his less-known writings, shed further light on his shifting approach to Islamic buildings in Egypt, embued in a marked ethnographic sensitivity and impacted by recurrent uncertainties.