A propped boulder "dolmen" in Quissett Woods

I was sure I had seen some writing by Mavor about this propped boulder in one of the upper valleys above the main kettle hole I wrote about here. I cannot find the reference.

Here it is in the distance, rockpile in the foreground:A stone wall runs from here down into the kettle hole to the right. I again remember Mavor writing about the directions that the stone "rows" follow on their way down into the hole. Closer up:There is a smaller wedge propping up the rock, to the upper right in this next picture:But check out the overhead view down:
That's a blast hole - something drilled out in order to place a charge inside the rock. But usually the blast splits a rock in the direction of the hole. Which did not happen here. Meanwhile, there are clear signs of steel drill splitting along the edges of the actual split. It is fun trying to imagine a chronological sequence of events that led to this structure. A person I showed it to thought it looked like a whale.

One more word about the rock pile in the first picture. Here it is again. It has one white cobble on its periphery (not visible in the photo) and is a bit nestlike:The pile is made from hundreds of small stones, quite different from all the other piles I saw in there.