The crossword solution for the term Emerson Opus is 'ESSAY'. Ralph Waldo Emerson was an American essayist, lecturer, and poet who led the Transcendentalist movement of the mid-19th century. His most famous work, 'NATURE', was published in 1836 and established him as a leading figure in the movement. Emerson's other works include 'The American Scholar' (1837), 'Self-Reliance' (1841), and 'The Conduct of Life' (1860). He is considered one of the most influential writers in American history.