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Results! Why, man, I have gotten a lot of results! I know several thousand things that won't work.
Thomas A. Edisondisputed·Edison: His Life and Inventions, by Frank Lewis Dyer and Thomas Commerford Martin·1910
Attribution contested
The famous form -- I have not failed, I have just found ten thousand ways that won't work -- has no source in Edison. The earliest record of the remark is this one, in the authorised 1910 biography, and it is a colleague's recollection of a conversation, not Edison writing. Note what changes in the retelling: several thousand becomes ten thousand, and a man cheerfully counting negative results becomes a man defending himself against failure.