Letter to Ralph Waldo Emerson
p259“Mickiewicz, the Polish poet, first introduced the Essays to acquaintance in Paris.”
Fuller, Margaret. The Letters of Margaret Fuller. Edited by Robert N. Hudspeth. Vol. IV. Ithaca: Cornell University Press, 1987.
Inferred Fuller identifies Mickiewicz explicitly as "the Polish poet" and admires him deeply, though she does not cite a specific work.