The Cathars were a Gnostic sect of southern (Languedoc) France in the 12th Century. "Perfecti" were individuals in the sect who followed the most extremely austere lives, renouncing worldly pleasures including eating of meat and sex. Did any diaries or writings from these Perfecti survive to modern times?
See Textes pour les cahiers du sud (1987) and Ecritures cathares (1968) by Rene Nelli.
The most famous tract is the The Provencal Ritual of the Albigeois published in facsimile by Jean Cledat: