Perched boulders

I used to wonder how perched boulders were balanced that way.  One explanation is that the glaciers dropped them into that position.  Then I used to think that someone dragged them into position, which would have been quite an engineering feat.  However, the answer is in the photo below.

See how the bottom of the boulder and the supporting bedrock were cut away?  The manitou is a chunk  of leftover stone.

Here is another perched boulder, which seems to be in danger of sliding off the bedrock ledge. Near this perched boulder is another one, with a large propped boulder to the rear.

Both of these perched boulders have long axis bearings of about 206 degrees.  This doesn't correspond to any astronomical events, but it is interesting that this nearby structure below has the same orientation. They don't seem to point to anything, either.

    The perched boulder below is a well-known feature in a RI state park.  It is obvious stone was gouged out to the right on this boulder. The long axis faces southeast.

Finally, here's another one,  with its long axis facing southwest.

All of these are on hilltops.  Creating these took a great deal of work, which I doubt a farmer would want to expend.  They were probably created by Native Americans, for some lost purpose.  Perhaps a hint comes from Indian legends, in which boulders are animated and capable of movement.  These boulders may have represented characters in Indian legends. Or they may symbolize the balance of life and nature.