SACRED STONE (Petra Sacra, Tabula Sacra; Gestatorium, Itinerarius, Viaticum). - A square or rectangular slab (25 x 30 cm.) consecrated by the bishop and containing a hollow for placing relics of holy martyrs; it serves as an altar on which to celebrate Holy Mass wherever there is no fixed consecrated altar.
It is called a portable or gestatory altar, because it is transportable from one place to another, especially suited for journeys (altare itinerarium, altare viaticum, lapis itinerarius); it is also called a superaltar, because it is inserted into a non-consecrated altar, whether movable or fixed. The CIC, can. 1197, 1, 2 prescribes that it be a single unbroken natural stone, large enough to contain the Host and the greater part of the chalice. It began to be used after Constantine, when the altar in the church, hitherto movable, became fixed and it was no longer permitted to celebrate Holy Mass outside a consecrated altar. The first reliable notices in the West are from the 6th century (from a letter of 511 addressed to two English priests who were going as missionaries to Brittany); but perhaps it was already in use, because in the letter it is regarded as something well known and necessary for celebrating Holy Mass on journeys. Then St. Bede recounts of the two Sts. Ewald, missionaries among the Saxons, who carried with them a table to take the place of an altar. In the first millennium, tables of stone or wood were used (for example, the oak table covered with silver plates found in the tomb of St. Cuthbert at Durham, Ireland); often the p. s. was inserted into the wooden table or framed in a wooden frame or box; sometimes, moreover, it was very small, of porphyry, onyx, rock crystal, or even slate; the relics were placed between the stone and the surrounding wood or in the wooden box. The latter are no longer permitted today (decr. aut. 3162 of 31 Aug. 1867). In the Middle Ages the rectangular form was preferred, sometimes also oval or round; then from the 15th century the square form. The dimension varies from 48.5 × 36.7 and 12.5 × 7.5 cm. (the smallest p. s. is that of Egbert's Portable at Trier and measures 2.4 × 2.4 cm.). St. Charles Borromeo prescribes 36 × 29 cm.; the code notes only a measure sufficient to contain the Host with the greater part of the foot of the chalice. In the consecration of a fixed altar there were never lacking relics to be included in the sepulcher; for portable ones, on the other hand, in the Middle Ages until the 13th century, there were no precise provisions. As signs of consecration, small crosses were inserted from the 15th century onward.
Outside a church or an oratory, public or semipublic, only those who have the privilege may celebrate Holy Mass on a portable altar.
Bibliography2 works
Pietro Siffrin