Thanks to its favorable position on the Via Cassia (one of the main ancient Roman roads), Bolsena was a usual halting place for all pilgrims coming from the North and bound for Rome to visit the sepulchres of Peter and Paul as well as those of the most renowned martyrs. The town is already mentioned in the itinerary of Sigericus (900-994), where Bolsena is remembered as Sancta Christina, from the name of its martyr, whose grave has been honored in the catacomb dug on the side of the hill since the most remote ages. Near this catacomb later were built the church devoted to the Saint, the hostels for pilgrims, the walls and towers for their defense, so that the place looked as a fortress of the faith.
In the year 1263 (the day is not known), maybe at the end of summer, a priest, whose name, according to tradition, was Peter, arrived at the sanctuary coming from the city of Prague (today capital of the Czech Republic). Tradition also reports that Peter had set out for such a long and difficult pilgrimage to strengthen his own vacillating faith, especially concerning the real presence of Christ in Eucharist.
Peter was strongly moved by the memory of the martyr Christine, whose faith did not waver in front of martyrdom. After having prayed with devotion on the tomb of the Saint, he celebrated the Eucharist on the same spot. During the Mass doubts began again to perturb his mind and his heart, and he prayed intensely the Saint to intercede for him with the Lord, that He give him her fortitude and unshakable faith. At the moment of consecration, after pronouncing the ritual words, from the host which he held over the chalice sprang out a lot of blood, which stained the corporal (the cloth on which consecrated elements are placed during celebration of mass). The priest could not go on officiating the ceremony and full of joy and commotion, wrapped the Eucharist in the corporal and retired into the sacristy. On the way some drops of blood also fell on the marbles of the floor and of the altar-steps.
After having recovered from his amazement, Peter, escorted by the clergymen of Saint Christine and by the witnesses of the Prodigy, betook himself to the near Orvieto, where at that time temporarily dwelled pope Urban IV with his court.
The priest confessed to the Pope his doubt asking for forgiveness and absolution. The sovereign pontiff sent at once Giacomo Malatraga, bishop of Orvieto, to Bolsena, escorted, according to the tradition, by the theologians Thomas Aquinas and Bonaventura from Bagnoregio, to check the facts and bring him back the relics. At the bridge of Rio Chiaro (nowadays Ponte del Sole ) the bishop, returning from Bolsena with the relics of the Miracle, met the Pope corning in procession to welcome him. The Pope was escorted by the clergy of Orvieto, the dignitaries of his court and a large crowd wavering olive-branches. Kneeling Urban IV received the host and the linens imbued with blood and brought them into the cathedral of Saint Maria, arousing everybody's commotion and joy. Here, after having shown the relics to the people, the Pope laid them in the sacrarium. Nothing was herd of the German priest ever since.
At the same time, during the stay of Urban IV in Orvieto, the pontiff established the feast of Corpus Christi by the bull Transiturus de hoc mundo on August 11th 1264 for the patriarchate of Jerusalem, and on September 8th for the universal Church. Thomas Aquinas was charged to write the office and the mass for the new feast that was to be celebrated on the Thursday after Trinity Sunday.
It is Urban IV himself who tells us that in Orvieto: together with all Archbishops and Bishops and high Dignitaries of the Churches dwelling in the Apostolic See, We solemnized the above mentioned feast, to give a salutary example to those present and to those remote who would hear of the celebration of this great day.
Iconographic and literary documents
In this way popular tradition handed down to posterity the story of the Miracle abundantly recorded by iconographic and literary docu-ments since the beginning of XIV century. The most ancient of them is an Orvietan chronicle where the Prodigy is related of already as the ...Miraculo del Corpus Domini... ("Miracle of Corpus Christi"). To the same time refers a very notorious miracle-play based on the event of Bolsena, which was performed every year in the town of Orvieto.
After that we find two stone-tablets engraved by Ippolito Scalza in 1573-71 for Bolsena and in 1601 for Orvieto, whose text relies upon a more ancient parchment from the half of the XIV century. To the same period refer two more ecclesiastical narrations: the Cathalogus by Pietro de' Natali (1369-1372) and the bull Quamvis cum from 1377. These two very ancient documents prove the renown of the Miracle outside of Bolsena and Orvieto and its close relationship to the establishment of the feast of Corpus Christi.
Of vital importance what concerns the historicity of the relics kept in Orvieto are the parchments which have accompanied them since the beginning (XIII-XIV centuries). During the following centuries we find plenty of popular and literary narrations of rather apologetic than historical importance.