Codex Calixtinus

The Codex Calixtinus (also Compostellus) is the main witness for the 12th-century Liber Sancti Jacobi, 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. It most likely date of compilation is the period of 1138–1145.

It was intended as an anthology of background detail and advice for pilgrims following the Way of St. James to the shrine of the apostle Saint James the Great, located in the cathedral of Santiago de Compostela, Galicia (Spain). The collection includes sermons, reports of miracles and liturgical texts associated with Saint James, and a set of polyphonic musical pieces. In it are also found descriptions of the route, works of art to be seen along the way, and the customs of the local people.

The compilation of Codex Calixtinus predates 1173, most likely taking place during the late 1130s to early 1140s. The compilation is most likely due to the French scholar Aymeric Picaud. Each of the five books is prefaced with a pseudepigraphic letter attributed to Pope Callixtus II (d. 1124). The appendix contains a letter by Pope Innocent II (d. 1143), presenting the finished work to Santiago. There are some clues suggestive of a later date of around 1160, but none of them render impossible a date of around 1140. The miracles in book II are recounted with their dates, between 1080 and 1135, so that the completion of the compilation can with some certainty be dated to between 1135 and 1173, and with highest probability to the 1140s.

...
Wikipedia