I had occasion to drive up Rt 3 to go to a job interview yesterday and I saw, to my dismay, that there are still a couple of stretches of woods along there where I have not been. In particular south of Treble Cove Rd on the east side of Rt 3 there is a thin stretch of woods. Well there was not much along there but there was a little: these knobs of outcrop by the highway had a couple maybe four little prayer seats which I could still make out. Also there was one place where the outcrop had obviously been quarried and piles of broken rock around the spot indicated someone had cleaned up a bit afterwards. And someone made a little outline from some of the fragments. Since this was just next to one of the "seats" I am thinking at the time after the quarrying, this place was still in use for ceremonies.
Here are a couple of seats. The third (and maybe even fourth) were more decrepit and are not illustrated. I did notice that each of them faced in opposite directions - sort of North, South, East, and West. This was just an impression. One interesting thing was comparing the coloring of the quarried rock with the ones in these pictures. These here were all uniformly gray, but sitting near some quarried rock which was still brown. The same brown color shows up a little further south in the stone walls and arrangements which appear to be a kind-of 19th century waste water treatement plant ruin, just north of the current waste water treatment facilities. So here is a place where a little color-based date ordering is possible.
By the way, if you drive north on Rt 3, look at the cut through the rocks on the right just before Treble Cove Rd. It is nice to know that there are prayer seats up there, remnants of what was there before.