Hildegard of Bingen (1098 to 1179) was a German Benedictine abbess, Christian mystic, composer, theologian, natural philosopher, and one of the most remarkable intellectual figures of the Middle Ages. From an early age, she reported experiencing vivid visions that she understood as revelations from God.
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."