One of the most ancient formulae of prayer at meals is found in a treatise of the fourth century, attributed without foundation to Saint Athanasius. Having made the sign of the cross, the prayer followed:

“We give Thee thanks, our Father, for the Resurrection which Thou hast manifested to us through Jesus, Thy Son; and even as this bread which is here on this table was formerly scattered abroad and has been made compact and one, so may Thy Church be reunited from the ends of the earth for Thy Kingdom, for Thine is the power and glory for ever and ever. Amen.”

From Catholic Encyclopedia.