St. Symeon the New Theologian (949-1022 AD) was a Byzantine Christian monk and poet, and was canonized as a saint by the Eastern Orthodox church. He wrote much about Christian mysticism, including his own experiences.
Henry David Thoreau (1817-1862) is widely known as a great 19th century transcendentalist essayist, poet, philosopher, naturalist, and historian, among other things. He is most well-known for his book Walden, and his essay "Civil Disobedience." The following comes from his poem titled "Inspiration."