Keeping donkeys for oral sex does not seem like the kind of thing you would normally associate with a travel guide, especially one dedicated to a pilgrimage, but sure enough there it is in the oldest guide book to the Camino, the twelfth-century Pilgrim’s Guide in the Codex Calixtinus:
In some places, like Vizcaya and Alava, when they get warmed up, the men and women show off their private parts to each other. The Navarrese also have sex with their farm animals. And it’s said that they put a lock on the backsides of their mules and horses so that nobody except themselves can have at them. Moreover, they kiss lasciviously the vaginas of women and of mules.
In condemning the loose morals of the people he encountered, the author reserved particular scorn for the Basques and Navarrese, and yet the Pilgrim’s Guide now has an important place in Basque scholarship, as it contains some of the earliest examples of the Basque language committed to writing.
The Pilgrim’s Guide is the fifth of the five sections in the Codex Calixtinus (Latin for “Callixtus’ Book”), which forms a kind of anthology on the cult of St James/Santiago, including accounts of miracles, legends and liturgies. Its alleged author was Pope Callixtus II (died 1124), who is known for (among other things) writing the papal bull Sicut Judaeis (a letter of universal protection for Jews) and restoring the Basilica of Santa Maria in Cosmedin, in Rome (which featured in the Audrey Hepburn-Gregory Peck film Roman Holiday). It’s not entirely clear why Callixtus should be associated with the Codex, but he had good connections with the lands of the Camino, as his brother Raymond of Burgundy married Urraca, heiress and future queen of León, and Raymond himself ruled Galicia under his father-in-law, in the 1090s.
The manuscript is now kept by the Cathedral of Santiago de Compostela and many of you who have completed your Camino may be familiar with it without even knowing — on your Compostela (certificate of completion) is an image of Santiago, hand raised in benediction, taken directly from the Codex Calixtinus. If that piques your interest you can buy some nice stationary featuring it in the cathedral shop, order a limited-edition facsimile – a steal at a mere €1900 online – or just steal the real thing like a disgruntled cathedral employee did in 2011!
 Denis Murphy’s very readable translation of the Pilgrim’s Guide (perhaps the most accessible translation in English on the internet), can be found here: https://sites.google.com/site/caminodesantiagoproject. The quotation is take from ‘Chapter VII. The lands and peoples along the Camino de Santiago’: https://sites.google.com/site/caminodesantiagoproject/chapter-vii
 ‘Cathedral thief gets 10 years for stealing 12th-century manuscript’, El País (18 Feb 2015): https://english.elpais.com/elpais/2015/02/18/inenglish/1424275570_591038.html