Houdon's Mask of Washington
Houdon’s portrait sculpture of Washington was the result of a specific invitation by Benjamin Franklin to cross the Atlantic specifically to visit Mount Vernon, so that Washington could model for him. Washington sat for wet clay life models and a plaster life mask in 1785.
Benson John Lossing, ed. Harper's Encyclopedia of United States History (vol. 4) (New York, NY: Harper and Brothers, 1912)