Josh says:
A couple of days ago you noted Elbruz.org's geographical claim, in this post:There is a larger one on Glover Island on Newfoundland.
I should know: I believe I'm the only person to have ever slept on an island on an island on an island. I went to Newfoundland once and camped on one the islands in the lake on Glover.
Link (This is a Google Maps link. Zoom in an out to see the island on an island on an island)