Letter to James F. Clarke
p169“mercilessly exhorted us to jump and run, (as it seemed to us), into the very arms of the vasty deep”
Fuller, Margaret. The Letters of Margaret Fuller. Edited by Robert N. Hudspeth. Vol. VI. Ithaca: Cornell University Press, 1988.
Inferred Fuller uses the phrase "vasty deep" as a casual allusion to Shakespeare's Henry IV Part 1, Act 3, Scene 1, where Glendower boasts "I can call spirits from the vasty deep."