The Copernican Revolution from the Inside

I stumbled across this saying, recently: The Cross is steady while the world is turning; Stat crux dum volvitur orbis. It's the motto of the Carthusians, a monastic order founded in 1084. But I can't figure out when they adopted that motto. And as I don't know Latin, I can't tell whether "volvitur orbis" refers to the Earth or the Heavens turning. Though the English translation sure seems to refer to the Earth, as does the naive translation of "dum volvitur orbis".

If the saying was from the 11th century (or even prior to the 15th century) and refers to the Earth, that would be interesting. I realize the heliocentric model existed long before Copernicus, but an early date to the motto would add more weight to arguments correcting misperceptions of the Copernican affair.

EDIT: Looks like it may have been adopted around 1600, when it first appeared on the Carthusian shield: https://books.google.com/books?id=gZaeGVNjIfcC&lpg=PA471&dq=...