Meditation Seats

Here is a small enclosure behind an outcrop in an area of Tiverton, RI, with many walls. The structure is about four feet across and  has partially collapsed. 

A  side view.

This is too small to have been  a house or storage shed.  There is no water nearby, so it was probably not a sweat lodge.  There don't seem to be any solar alignments, either.
 In the background is a wall

What could this small structure be?
Here is another small enclosure in RI, in an area with many cairns, as well as  building foundations and quarries.

Here is one in  Sharon, MA,  near an old cabin. This one is constructed of stacked cobblestones and decorated with a rusty oil drum.

 Here is another of these enclosures, presumable from a later period since it is constructed of  cinder blocks.

And here is what these might have been. If this wooden outhouse was removed, the outline of bricks and stones in the foundation would be very similar to those above.  The door side of all these enclosures is open.

Although the first enclosure shown above is partially collapsed, it is easy to imagine the wooden outhouse structure resting on the stones, with the large stone to the left acting as a step to the door. A Google Images search of "prayer seat" turned up many images of these square-cornered small enclosures from the northeast.  I even saw a small squarish stone enclosure at the Pequot Museum at Foxwood, in a reconstruction of an early 19th century reservation farm site.  The marker said the purpose was unknown.  Once every farm had at least one. The prayer seats shown in Mavor & Dix are rounded. Maybe these square structures should be called meditation seats, since they supported a  "Meditation Room".