“Warlocks are independent. And hard to get hold of. Like cats, but with fewer tails. Well, there are some tails. I don't have one myself”

This is from Pickings from the Porfolio of the Reporter of the New Orleans "Picayune" (1846) by Dennis Corcoran; it seems to have become attributed to Crockett in The Dictionary of Biographical Quotation of British and American Subjects (1978) by Richard Kenin and Justin Wintle, p. 206
Misattributed

Source: The Book on the Taboo Against Knowing Who You Are (1966), p. 26-27

"I've Got A Tiger By The Tail"

Source: The Particular Sadness of Lemon Cake

Account of his famous dream of the benzene structure, as quoted in A Life of Magic Chemistry : Autobiographical Reflections of a Nobel Prize Winner (2001) by George A. Olah, p. 54<!-- also partially quoted in Serendipity, Accidental Discoveries in Science (1989) by Royston M. Roberts , pp. 75-81 -->
Context: I was sitting writing on my textbook, but the work did not progress; my thoughts were elsewhere. I turned my chair to the fire and dozed. Again the atoms were gamboling before my eyes. This time the smaller groups kept modestly in the background. My mental eye, rendered more acute by the repeated visions of the kind, could now distinguish larger structures of manifold conformation; long rows sometimes more closely fitted together all twining and twisting in snake-like motion. But look! What was that? One of the snakes had seized hold of its own tail, and the form whirled mockingly before my eyes. As if by a flash of lightning I awoke; and this time also I spent the rest of the night in working out the consequences of the hypothesis. Let us learn to dream, gentlemen, and then perhaps we shall learn the truth... but let us beware of publishing our dreams before they have been put to the proof by the waking understanding.

Source: Uncommon Criminals

Letter (1 April 1935); published in The Letters of T.E. Lawrence (1988), edited by Malcolm Brown.