Letter to Alexander Ireland
p231“To the new fraternity I think we belong whose glory is service, whose motto Excelsior.”
Fuller, Margaret. The Letters of Margaret Fuller. Edited by Robert N. Hudspeth. Vol. IV. Ithaca: Cornell University Press, 1987.
Inferred Fuller writes "whose motto Excelsior," using this Latin word as a rallying cry for a progressive, service-oriented fraternity.