I was sitting in a chair in the patent office at Bern when all of sudden a thought occurred to me: If a person falls freely he will not feel his own weight. I was startled. This simple thought made a deep impression on me. It impelled me toward a theory of gravitation.

Source:Einstein in his Kyoto address (December 14, 1922), talking about the events of 'probably the 2nd or 3rd weeks' of October 1907.
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