Original 1913 document for Nikola Tesla's fluid propulsion patent, filed on 21 October 1909. Document is a U.S. Patent Office affidavit by Tesla's assistant, engineer Fritz Lowenstein. Within the report, Lowenstein attests to tests performed by Tesla related to his turbines, in support of the patent, which transformed mechanical power through the agency of fluid. Document runs 10pp. including cover, and measures 8'' x 11.25''. Fold and light wear, overall very good condition.