Liber Diurnus ROMANÔRUM PONTIFICUM is the name given by the see of Rome to a collection of formulas used in its correspondence and other business transactions. These formulas are very like those written for secular affairs by the monk Marculph (about 660) and others, and received from the compiler the name of Liber Diurnus because they relate to negotia diurna (see Marino Marini, Diplonmatica pontifiscia, ed. nov. Romans 1852 sq., page 64). They are interesting as scientific and historical monuments as well as for their practical use; and this is specially the case with the Liber Diurnus Pontificalis, which contains copies of the letters addressed by the Roman bishops to the emperor, the empress, consuls, kings, patriarchs, bishops, and other members of the clergy, and in general to all who were in any way concerned in the nomination of the Roman bishops; the professio pontificia, the exemptions granted on the occasion of nominating neighboring bishops, on bestowing the pallium (q.v.), conferring privileges and immunities, etc. On all these points, and the manner in which these things were practiced from the 6th to the 8th century, the Liber Diurnus contains more or less complete information, particularly on the relations existing between the see of Rome and the emperor, the mode of election of the Roman bishops, the ritual, etc. To judge from its contents, this collection was probably written before the year 752, for it speaks of the relation between the see of Rome and the eparchs, who were abolished in that year; but, on the other hand, it must be posterior to 685, for in caput 2, tit. 9, the emperor Constantine (Pogonatus) is spoken of as being already dead. It must also have been written under some successor of Agatho (t 682), as this Roman bishop is also mentioned as dead. Garnerius supposed it to have been composed in the time of Gregory II, somewhat after 714, on the ground that in the second professio fidei pontificis, given in the Liber Diurnus, there are expressions and views which correspond exactly to those we find in the letters of that pope to the emperor Leo. It is likely, though, that the Liber Diurnus existed originally in a more elementary form before it assumed that under which it is known at present, for the different MS. copies of it differ somewhat from each other. The Liber Diurnus was frequently consulted by all writers on canon law, such as no of Chartres, Anselm of Lucca, Deusdedit, Gratian (c. 8, dist. 16). As the ritual and various points of law underwent modifications in the course of time, it was less used, and its existence even came to be concealed by the popes for fear lest it might recall their former dependence upon the emperors and eparchs. Still there were copies of it in existence, and a codex contained in the library of the Vatican was published in 1660 by the care of Lucas Holstenius; it was, however, at once suppressed by the Roman see. Hoffmann (Novas collectio scriptorum ac monumentorum, Lipsiae, 1733, 4to, 1:389) attributes to Baluze (in the remarks on Petrus de Marca, De concordia sacerdotii ac imperil, lib. 1, cap. 9, No. 8) the statement that at the time of Holstenius the Vatican library possessed no codex of the Liber Diurnzus, and that his publication was based upon a MS. entrusted to him by the Cistercian monk Hilarius Rancatus. But as both editions of the works of P. de Marca, published at Paris by Baluze, state only (lib. 2, cap. 16, No. 8) that Holstenius's publication of the Liber Diurmus was suppressed, and Baluze again, in his notes appended to Anton. Augustinus, De emnendatione Gratiani, lib. 1, dialogus 20, § 13 (ed. Par. 1760, page 433), says that there were various copies of the Liber Diurnus in existence, from one of which, that in the Vatican library, Holstenius published his edition, it seems reasonable to suppose that Hoffmann's statement lacks support. As for Rancatus, Mabillon names Leo Allatius, and not Holstenius, as the party to whom he imparted the MS. (see also Cave, Scriptorum eccl. hist. literaria, Basle, 1741, 1:621). The MS. of the Vatican has actually been described by Pertz (Italienische Reise, in Archiv. f. altere deutsche Geschichtskunde, 5:27). He says that it is an 8vo volume of parchment,and that, according to the statement found on its firstpages, it dates from the 8th century. The Jesuit Joannes Garnerius, with the aid of a similar codex and a MS. found in Paris,. published in 1680 another edition of the Liber Dimurnus, "cum privilegio regis Christianissimi." Mabillon, in the Museum Italicum (folio II, 2:32 sq.), published additions to it by means of the MS. which had been used by Leo Allatius. With the aid of all these works, Hoffmann published a new edition of it in the Nova collectio cit. (volume 2), which was subsequently done also by Riegger (Vienna, 1762, 8vo). All this gave rise afterwards to collections of formulas to replace the obsolete Liber Diurnus. There are several such collections still extant in MS. Among them the Formulariumn et stylus scriptorum curiae Romanae, from John XXII to Gregory XII and John XXIII, in Summa cancellaria Joannis XXII. We may also consider as belonging to this class of works the Rituum ecclesiasticorum sive
ceremoniarum libri tres of bishop Augustinus Patricius Piccolomini, printed by Hoffmann (2:269 sq.), and containing a description of the rites accompanying the election of the popes in the 14th century. Collections of formulas similar to the Liber Diurntus were also made for the use of bishops, abbots, etc. See Rockinger, Nachweisunqen über Formelbücher v. xiii-xvi Jahrhund. (Munich, 1855, pages 64,126,173, 183, etc.); Palacky, Ueber Formelbücher (Prague, 1842); Herzog, Real-Encyklop. 8:366; Wetzer u.Welte, Kirchen-Lex. volume 5, s.v.