Liber instrumentorum memorialium

The Liber instrumentorum memorialium is the surviving cartulary of the Lords of Montpellier, the Guilhems (Guillems), and an important source for their history.

The last few documents record the brief independent rule of William VIII's daughter Mary before her marriage (15 June 1204) to Peter the Catholic brought the lordship into the Crown of Aragon.

On the exceptional completeness of the cartulary of the Guilhems, Archibald Ross Lewis wrote:[5] The Cartulary of the Guillems of Montpellier presents an unusually full record of the activities of a noble family of southern France between the last decades of the eleventh century and the earliest years of the thirteenth.

The Cartulary is preserved primarily because after 1204 most of the heritage of the Guillems was taken over by the commune or town of Montpellier in a corporate sense.

[8] The Liber also gives evidence of the weakness of the King of France in the south of his realm during the twelfth century, when he figures only as a tool for dating documents; real authority lay with the Popes.