Pope Callixtus II
The ' (also "Compostellus") is the main witness for the 12th-century ', or the Book of Saint James. It is a pseudepigraph attributed to Pope Callixtus II; its principal author or compilator is referred to as "Pseudo-Callixtus", often identified with French scholar Aymeric Picaud. Its most likely date of compilation is the period of 11381145.