At Cryhelp, three miles on the east side of Dunlavin, is a granite rectangular stone 6 feet high. It is 1 foot wide at its base and 9 inches near the top; 1 foot 9 inches from the apex the stone is pierced through by a rectangular hole 9 inches by 4 1/4 inches and facing east and west.
[...] Locally the stone is believed to mark the grave of Prince Aralt (Harold) one of the Danish Chieftains killed in the Battle of Glenmama. If we are to take it that the valley near this district was not the site of the Glenmama Battle, then one must conclude that this stone does not mark Prince Harold's grave. Local tradition holds that the corner where this stone stands was formerly a cemetery covered with trees and that this stone once occupied another place in the corner in the field, being removed to its present site to mark the grave of Prince Harold. Many residents state that the cemetery was known as "Crushlow Churchyard."
The stone has certainly a tradition and, on account of the hole in it, it is of interest, but, beyond the fact that marriages were once celebrated at it, there exists no account relative to any curative or other properties being associated with this monument.
(N.B. In the adjacent field on the north side is a nettle-covered hollow. This has been opened and a passage was discovered underneath leading in a northerly direction. It is said that the passage communicates with what is apparently a destroyed mound in the northern corner of the field on the opposite side of the road. In some parts one can stand erect within it. Those who have been in the tunnel state that their clothes were covered with a fine flour like mould on exit).
So much folklore for a stone that looks essentially like a gatepost. But what do I know. Let me know if it's not really old.
From 'The Antiquities of the Dunlavin-Donard District (Counties of Wicklow and Kildare)' by Patrick T. Walshe, in The Journal of the Royal Society of Antiquaries of Ireland, 7th series, Vol. 1, No. 2 (Dec. 31, 1931).