My only familiarity with this practice (the classic horror "Nosferatu"
opens with the dirt being cleared away from one, I believe) is an
inadvertently disturbed Shaker cemetery in Kettering, Ohio, south of
Dayton. The community, on about 900 acres was called "Watervliet"
after the town on the west bank of the Hudson River where the founder
of the "Shaker" movement was buried. (Today, Watervliet, NY is more
known as an advanced weapons development and testing facility, started
I think in the 19th century, an interesting paleo point turned up in
required testing there).

The problem there was that the property was to become a research
facility, and one of the first to build there was Dayton Power and
Light, who I think may also provide the electric overhead lines that
provide buses all over the place. Dayton is the largest Air Force
facility in the country, and the museum there is very interesting,
chronicling the developments of the nearby Wright brothers, a part of
their original plane was left on the Moon by US astronauts, and has
large planes on exhibit like the "Black Widow" its restoring, the
first automated machine gun on its top.

The surveyors had described in the past where the Shaker cemetery was
supposed to be, they have no stone markers, except perhaps one
(Canterbury Village, NH) which was placed as could be deduced in the
wrong place, on top of a hill of glacial till, next to their orchard
(they sold seeds, brooms, and invented a condensed milk in the very
early 20th century) instead of in a lower area, and it was hit by
machinery, the phase of which I was not involved in, but where the
"coffin window glass" and other hardware was recovered which surprised
some.

I dug 2.1 miles of backhoe trenches in close proximity with two others
and three backhoes in ten days, one hot September, after ground
penetrating radar was conducted by Bruce Bevan around the monument
just placed. We had a surveyor marker to work from (for the monument)
and using an electron it transit I was able to provide the
documentation "clearance" at the end of ten days on paper for Dayton
Power and Light, which they said "there goes our computer-aided design
budget" referring to the efforts cost.

My understanding was that the design of those coffins was in the late
19th early 20th century, and the gentleman form Power and Light
thought that the monies from their inventions had been spent a little
less frugally than one would have thought for the glass.

George Myers