I wonder do Law Libraries have anything like a searchable database of wills? The thought is that perhaps somewhere, in some will, a landowner specified that a part of their property containing Indian structures should be preserved. If Law Libraries have such a database, some kind of search on this topic would be worth doing.
I read through some early Wampanoag Land deeds online and they did mention rock piles. So the question about wills is a variant of the same idea.