Strangest Propped Boulder Yet

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Somewhere in Northern RI, a stream is dammed to form a small pond.

The water flows out of a small opening in the wall.  There are no building foundations, so it does not look like there was a mill here.

Further upstream, and leaning against an outcrop, is a very strange propped boulder.  One end is nearly square, and about 2 feet on each side.

This side view shows it has its own bent tree, and a strange shape, like an  old TV picture tube. Usually propped boulders are oblong with smooth contours.

Also, the other propped boulders in this area are on top of hills, not in a low area near a stream.
     This shape does not look natural, so  it may have been quarried from a larger boulder at this outcrop. Note that the supporting stone is pointed, and has very little contact with the propped boulder.  Usually  supporting stones are rounded or square.  The pointed supporting stone could have been used to allow greater access to the lower part of the boulder for carving, or for some ceremonial use.  Whether this shape was intentional, or if this was a work in progress, is a mystery.