“Unperformed experiments have no results.”

Letter to David Hartley (2 July 1787) https://founders.archives.gov/documents/Jefferson/01-11-02-0441 <br class="br">1780s <br class="br">Context: I have no fear that the result of our experiment will be that men may be trusted to govern themselves without a master. Could the contrary of this be proved, I should conclude either that there is no god, or that he is a malevolent being.

Source: The Power

Letter to his wife, reprinted in Rilke’s Letters on Cézanne (1952, trans. 1985). (June 24, 1907)
Rilke's Letters

Ce n'est point l'observation mais la théorie qui m'a conduit à ce résultat que l'expérience a ensuite confirmé.
explaining how he was led to discover the law characterizing interference fringes, in [Œuvres complètes d'Augustin Fresnel, Imprimerie impériale, 1866, http://books.google.com/books?id=3QgAAAAAMAAJ, 61]

Words I Wish I Wrote (1997)
Context: My convictions have validity for me because I have experimented with the compounds of ideas of others in the laboratory of my mind. And I've tested the results in the living out of my life. At twenty-one, I had drawn an abstract map based on the evidence of others. At sixty, I have accumulated a practical guide grounded in my own experience. At twenty-one, I could discuss transportation theory with authority. At sixty, I know which bus to catch to go where, what the fare is, and how to get back home again. It is not my bus, but I know how to use it.

Source: [Wiener, N., A New Theory of Measurement: A Study in the Logic of Mathematics, Proceedings of the London Mathematical Society, s2-19, 1, 1921, 181–205, 0024-6115, 10.1112/plms/s2-19.1.181]

Source: Quantum Reality - Beyond The New Physics, Chapter 11, The Einstein-Podolsky-Rosen Paradox, p. 199 (See also: John Stewart Bell)