From the History of the Indians of Connecticut by John DeForest first published in 1851 (reprinted 1964 by the Shoestring Press in Hamden CT).
In Chapter “X,” “History of New Tribes formed in the North and West of Connecticut (DeForest claimed that this part of the state was previously uninhabited by Indians and was a great “desert”),” I found this stone mound reference:
“The sites of Indian cemeteries are still pointed out in New Milford. One is on the west side of the river opposite the village; another is on the east side at no great distance from the ancient residence of the sachem. Many of the graves have trees of considerable size growing up out of them. The mounds are circular in shape, and, on opening them, the skeletons are found in a sitting posture. The grave of Weraumaug is still supposed to be known, and differs from the others only in being of larger dimensions (398).”
There is an asterisk after the last word in the paragraph and the footnote reads, “Barber, pp. 475,476.”
There must be an illustrated version because this is included in Enduring Traditions, edited by Laurie Weinstien (1994) in the section by Trudie Lamb Richmond: see attachment.