“Wait a minute! I am not a mystic. Trying to find out the laws of nature has nothing to do with mysticism, though in the face of creation I feel very humble. It is as if a spirit is manifest infinitely superior to man's spirit. Through my pursuit in science I have known cosmic religious feelings. But I don't care to be called a mystic.”

Draft of a German reply to a letter sent to him in 1954 or 1955<!-- (also not known if this reply was sent) -->, p. 39
Attributed in posthumous publications, Albert Einstein: The Human Side (1979)
Context: I have never imputed to Nature a purpose or a goal, or anything that could be understood as anthropomorphic. What I see in Nature is a magnificent structure that we can comprehend only very imperfectly, and that must fill a thinking person with a feeling of "humility." This is a genuinely religious feeling that has nothing to do with mysticism.

Source: The Nature of the Physical World

Art Psalms (2008), Seven Statements on Mystic Art

LSD: The Geek's Wonder Drug? (2006)

Letter to Phyllis Wright (January 24, 1936), published in Dear Professor Einstein: Albert Einstein's Letters to and from Children (Prometheus Books, 2002), p. 129
1930s

Science and the Unseen World (1929), IV, p.47

Quote of Jawlensky from a letter to his brother Dimitri, c. 1917/18; as cited in Alexej von Jawlensky, Museum Boymans-van-Beuningen, Rotterdam; exhibition catalog 25/9 – 27/11-1994, p. 150
1900 - 1935

Our Christ : The Revolt of the Mystical Genius (1921)