ANTIMENSION. — It is the portable altar of the Greeks. In time, the Latin Church adopted only portable stone altars, whereas the Greek Church made use of wood and also of cloth, eventually using only the latter. Today the antiminsion is commonly a rectangle (sometimes a square) measuring 0.40 x 0.60 m., of silk or even canvas, bearing sewn onto its reverse side a small pouch containing relics, placed there by the bishop at its consecration. It originated in the frequent need to celebrate the divine mysteries far from churches, or in places lacking fixed altars; but positive historical data are available only from the 8th and 9th centuries. Formerly it was used only when the altar was not consecrated; today, however, it is used indiscriminately on all altars. Outside Mass, it remains on the altar folded in four; during the celebration of the divine sacrifice, the priest unfolds it at the proper time according to the rubrical prescriptions. It is ordinarily consecrated during the ceremony of the consecration of a church, when the bishop, having washed the altar a second time
with perfumed wine or rose water, dries it with the antiminsia, and then repeats the same action after anointing the altar with sacred chrism. The antiminsia thus consecrated must remain on the altar until seven Masses have been celebrated upon II. In cases of necessity, they may also be consecrated at other times by the bishop or by a priest delegated for this purpose. Priests of another rite are forbidden to celebrate Mass upon the antiminsion (can. 823, § 2).