Which preposition to use with essenes

at Occurrences 1%

While according to Josephus the party of the Essenes at one time numbered four thousand, like all ascetic movements it soon disappeared or else was deflected into that greater stream of monasticism which rose in the early Christian centuries.

in Occurrences 1%

It was also used by the Essenes in their sacred rites, and by the Egyptians as a pass-word.

Which preposition to use with  essenes