Everything published about the Sarmoung Brotherhood descends from Meetings with Remarkable Men, the second of Gurdjieff's three books, and from what he said to pupils. In that account the name is first met in an old Armenian manuscript, and the search for the body it names runs through years of travel with a group he calls the Seekers of Truth. Eventually he and a companion are led to it: taken by guides, blindfolded for the last stage of the journey, and brought to a monastery in a remote valley in Central Asia.
What he describes seeing there is chiefly a form of sacred dance, performed by women on a set of wooden apparatus that placed the body in precisely fixed positions, the sequences understood as a notation carrying knowledge in movement rather than in words. That description is the stated origin of the movements Gurdjieff later taught in Europe.
Two things about the source need stating plainly. The book is written as autobiography but does not behave like one: dates are absent or impossible, the geography is vague at exactly the points where it would be checkable, and the episodes are shaped like teaching stories. Gurdjieff himself described his writing as deliberately constructed in layers, meant to resist a single literal reading, and pupils were told as much.