I was under the impression that this bullaun stone had only been rediscovered in the last few years. However this map http://www.visitclare.net/gfx/HImonastic.jpg relating to Macalister shows it clearly and I under this dates back to 1916-17.
I've grew up on the other side of the lake and some of my early memories are of heading out to picnics on this island.
However it was only last year when I got a boat over, from local tour Mountshannon guide Ger Madden (he gave me a lovely tour pamplet to review which showed this bullaun) that I knew of this particular bullaun.
From the eastern landing site you will need wellies to walk along the shore-line until you come to this bullaun.