"The only unnatural sexual behavior is none at all." To whom is this quote attributed?

Explanation

The Jewish-Austrian neurologist Sigmund Freud (1856-1935) founded the discipline of psychoanalysis. He is considered to be amongst the foremost thinkers of the 20th century. Freud worked with hypnosis, psychoanalysis and dream interpretations. Amongst his most famous quotes are the following: (1) "The only unnatural sexual behavior is none at all." (2) "The great question that has never been answered and which I have notyget been able to answer, despite my thirty years of research into the feminine soul, is "What does a women want?" (3) "We must reckon with the possibility that something in the nature of the sexual instinct itself is unfavorable to the realization of complete satisfaction".