4. It is not Our purpose here to append a long disquisition on the numerous visits of kings, bishops, prelates, and faithful on continual pilgrimages to the tombs of the Apostles, particularly since several famous scholars have previously treated this whole subject. We refer of course to Onuphrius Pavinus in his treatise On the Eminence of the Basilica of the Vatican, which We read often before its publication as it rested safely in the archives of the basilica. At the time, We were still among the lesser clergy, that is, appointed to the canons of the Vatican basilica and acting as Prefect of the Archives of this basilica; We refer also to Jacobus Gretserus, de sacris Peregrinationibus in tome 4, bk. 2, chap. 12ff, of the new edition of his works; Coccius, Thes. Catholic., bk. 5, chap. 17; Stanislaus Hosius, cap. de Caeremoniis; Rutilius Benzonius, de anno Sancti Jubilaei, bk. 6, chap. lf; Drexellius, tome 13, part 1, chap. 7, pp. 126ff of the Monachian edition; and quite recently Trombelli, de Cultu Sanctor, tome 1, pt. 2, chap. 46f. But the formula of the monk Marculf who lived in the seventh century is never mentioned by the above writers. His formula describes the way letters of recommendation, written for those setting out on pilgrimages, should be composed. These letters are addressed to the supreme pontiff and to bishops. This formula is to be found in bk. 2, chap. 49, and reads as follows: "The bearer of this, considering hard and toilsome journeys of little account, not because of idleness (others read: for the sake of wandering) but in the name of the Lord, and desirous of approaching the tombs of the blessed apostles of the Lord, Peter and Paul, to gain the benefits of their prayers, has asked me in my littleness to recommend him to your kindness". St. John Chrysostom writes thus on this subject: "in the royal city of Rome emperors, consuls, and military commanders hasten without their retinue to the tombs of the fisherman and the tentmaker" (Quod Christus sit Deus, tome 1, p. 570, no. 9, Paris, 1718). Eginhard testifies that the emperor Charlemagne in the course of forty-seven years, under the spur of devotion, came to Rome four times, saying: "Charlemagne, within a span of forty-seven years, travelled to Rome to pray and accomplish what he had vowed". And We must mention the fine testimony of Nicholas 1, who flourished in the ninth century, which records the very numerous pilgrimages to this city in honor of the blessed remains of the Apostle Peter. "So many thousands of men hastening from every region of the earth betake themselves daily to the protection and intercession of blessed Peter the prince of the Apostles, and purpose to remain near his tomb to the very end of their lives. By analogy with the incident recorded in Acts when the vessel was let down from heaven in which all kinds of living things were shown to this same Blessed Peter who is their guide, the Catholic Church is signified by the City of Rome alone, in which the bodily presence of this Apostle is carefully reverenced, and which contains as in a vessel all nations of all animals (whose spiritual significance is men)" (Epistle 8 to Emperor Michael).