“Remember that your brain is no more developed by the thoughts your husband thinks than your body is nourished by the food your husband eats.”

Letter to John Adams (31 March 1776), published in Familiar Letters of John Adams and his wife Abigail Adams (1875) edited by Charles Francis Adams, p. 147
Context: I long to hear that you have declared an independency. And by the way, in the the new Code of Laws which I suppose it will be necessary for you to make I desire you would Remember the Ladies, and be more generous and favourable to them than your ancestors. Do not put such unlimited power into the hands of the Husbands. Remember all Men would be tyrants if they could. If particular care and attention is not paid to the Ladies we are determined to foment a Rebellion, and will not hold ourselves bound by any Laws in which we have no voice, or Representation.
That your Sex are Naturally Tyrannical is a Truth so thoroughly established as to admit of no dispute, but such of you as wish to be happy willingly give up the harsh title of Master for the more tender and endearing one of Friend. Why, then, not put it out of the power of the vicious and the Lawless to use us with cruelty and indignity with impunity? Men of Sense in all Ages abhor those customs which treat us only as the vassals of your sex; regard us then as Beings placed by Providence under your protection, and in imitation of the Supreme Being make use of that power only for our happiness.

The Saviors of God (1923)
Context: You are not a miserable and momentary body; behind your fleeting mask of clay, a thousand-year-old face lies in ambush. Your passions and your thoughts are older than your heart or brain.

Source: The Way Toward Health (1997), p. 259

Source: Gone Girl

Source: Jonathan Livingston Seagull

Source: The Joy Luck Club (1989), Ch. 1, pg. 26

Dates to 1899, American humor origin, originally featuring a woman upset by a man's cigar smoking. Cigar often removed in later versions, coffee added in 1900. Incorrectly attributed in Consuelo Vanderbilt Balsan, Glitter and Gold (1952).
See various early citations and references to refutations at “If you were my husband, I’d poison your coffee” (Nancy Astor to Churchill?) http://www.barrypopik.com/index.php/new_york_city/entry/if_you_were_my_husband_id_poison_your_coffee_nancy_astor_to_churchill, Barry Popik, The Big Apple,' February 09, 2009
Early examples include 19 November 1899, Gazette-Telegraph (CO), "Tales of the Town," p. 7, and early attributions are to American humorists Marshall P. Wilder and De Wolf Hopper.
Churchill by Himself: The Definitive Collection of Quotations, by Richard Langworth, PublicAffairs, 2008, p. 578.
The Yale Book of Quotations, edited by Fred R. Shapiro, New Haven, CT, Yale University Press, 2006, p. 155.
George Thayer, The Washington Post (April 27, 1971), p. B6.
Misattributed
Variant: Lady Nancy Astor: Winston, if you were my husband, I'd put arsenic in your morning coffee.

Winston Churchill: Madam, if you were my wife, I'd drink it.

On marriage, p. 118
Photoplay: "Wedded and Parted" (December 1922)

Source: A Fatal Grace