Britain's Prince Charles and Camilla, Duchess of Cornwall, visit the Lincoln Memorial in Washington, March 18, 2015. The couple is scheduled to visit cultural and educational sites over the next three days. [Photo/Agencies]

WASHINGTON - Prince Charles learned something new on his tour of the nation's capital Wednesday: His uncle built a better polo stick.

Charles and his wife, Camilla, got the royal tour of the US capital, being ushered around Washington's monuments and memorials on the National Mall by a handful of American luminaries.

It was on a tour of the National Archives, though, where Charles was genuinely surprised and delighted. National Archivist David Ferriero presented the prince with a patent application submitted in 1931 by his uncle, Lord Louis Mountbatten, for a new kind of polo stick.

Charles, himself a polo player, laughed and said he had no idea that his uncle had designed a polo stick.

He also laughed when shown a telegram from the US embassy in London to the Secretary of State, sent in 1957 seeking instructions to ensure that a toy car that had been given to Charles, then 8 years old, would be working properly when he returned home to play with it.

Earlier in the day, at George Washington's Mount Vernon estate, Charles and Camilla toured the iconic mansion overlooking the Potomac, and paid tribute to the Founding Father who, more than anyone else, ensured that Americans would not be British subjects.