On the origin of the stone:
There are at present the remains of two ancient churches at Ardmore. One situated on the edge of a cliff near the sea, which is quite in ruins, and seems to have been the first church built hereabouts; near which on the Strand, they shew you St Declan’s stone, as it is called, being of a coarse grit, like all the adjacent rocks. It lies shelving upon the point of a rock, and on the patron-day of this saint, great numbers creep under this stone three times, in order, (as they pretend,) to cure and prevent pains in the back.
This stone, they tell you, swam miraculously from Rome, conveying upon it St Declan’s Bell and vestments.
Near this church is a Well dedicated to the same saint, to which, as well as to the stone, many miraculous virtues are attributed by the superstitious people.
The Ancient and Present State of the County and City of Waterford, by Charles Smith (1746).