Visited 25th July 2003: On my way to my brother's Stag do, I detoured into Welshpool to find Maen Llog. At first I got the wrong church, and when I eventually found St. Mary's Church, parking turned out to be a bit tricky. One of the two gates into the churchyard was locked, but once I'd found a way in the stone was obvious.
Maen Llog is very polished, presumably by people standing on it for various reasons, over the centuries. It looks rather inconsequential, standing as it does among the gravestones. Worth a visit if you're in the vicinity, if only because of the numerous rituals attributed to it.
In his book More Mysterious Wales, Chris Barber writes:
Standing in the churchyard [of St. Mary's Church, Welshpool], this hunk of stone is reputed to have stood formerly in the abbey of Strata Marcella (SJ25131042) where the abbots were 'installed' on it as part of a well established ritual.
After the Dissolution of the monasteries Maen Llog was moved to St. Mary's Church, and a new ritual grew up around it:
Folk who were required to do penance were made to stand on the stone, dressed in a white sheet, with a candle in one hand.
The stone was moved into the graveyard on the instruction of a Puritan called Vovasour Powell, who considered it to be an object of superstition. It sounds like Powell was right, because the stone came to be used as a wishing stone. To make wish, you have to climb it and turn three times to face the sun.
Clwyd Powys Archaeological Trust list Maen Llog in its current position, as a 'boulder' of unknown date. It's antiquity must be in doubt, as nobody else seems to list it. It really doesn't look much like a standing stone (Barber's hunch), but it does remind me of a photo I've seen of Carreg Pumpsaint which is thought to be a possible anvil stone (Roman or Medieval). This is just supposition of course.