Leaflets or small booklets containing the prayer formularies (e.g., the collect and other presidential prayers, the preface to the Roman Canon, the introductory formula for the Hanc igitur, etc.) that were composed for specific Sundays or feast days. They are significant as the bridge marking the transition from the period of extemporized praying, and the collection and arrangement of presidential prayers into a sacramentary proper.
It appeared that North African synodal legislation encouraged the individual bishop to write down his formularies of liturgical prayer. During the course of the fifth and sixth centuries individual bishops began to gather together such collections, to which the name Libelli Missarum has been given. Some bishops had recourse to the Lateran Archives, which contained the Libelli Missarum of many of the popes. Now, from the time of Pope Damasus (366–384), Rome had enhanced the cult of the martyrs. However, such a cult was a strictly local one, the Mass of the martyr being said only in the place of his burial or his church. In the tituli, or parish churches, the Mass formularies used were exclusively of the type now in the Roman Missal for use on Sundays. During the pontificate of Leo the Great, the tituli began, for some reason unknown to us, to celebrate the feasts of the martyrs— and in the churches of the martyrs they began to make use of the Masses of the Temporal. It was at this time that the first Roman Libelli Missarum began to appear. It must be stressed that at this period (mid-fifth century) Rome possessed no Sacramentary for general use—neither during the pontificate of Leo I nor during that of Gelasius. There would have been no call for such a book, since each church had its own small collection of Mass formularies. H. Schmidt has suggested ["De Sacramentariis Romanis," Gregorianum 34 (1953) 729], and the idea is not without some probability, that Gelasius I gathered together a number of these Libelli Missarum and that this collection later formed the nucleus of the official Roman Sacramentary. A study of these prayer formularies is indispensable to an understanding of liturgical development in the Latin rite.
While individual examples of libelli missarum are no longer extant in most cases, a single-volume compilation of these libelli have survived, and is popularly, though incorrectly known as the leonine sacramentary.
Bibliography: c. vogel, Medieval Liturgy: An Introduction to Sources (Washington, D.C. 1986). e. palazzo, A History of Liturgical Books: From the Beginning to the Thirteenth Century (Collegeville, Minn. 1998).