Book of the Secret Supper

The Book of the Secret Supper (Cena Secreta), also known as Interrogatio Iohannis (The Questions of John), The Book of John the Evangelist and The Gospel of the Secret Supper was a Bogomil apocryphal text from Bulgaria, possibly based on a now lost Paulician treatise, which also became an important Cathar scripture. The book was translated into Latin and introduced to Italy in the late 12th century, then taken to Provence before the Albigensian Crusade by the Cathar bishop Nazarials or Nazario.

Source: Wikipedia — Book of the Secret Supper (CC BY-SA 4.0)