Capitol cornerstone

On a wall in the U.S. Capitol is this mural painted by Allyn Cox (1896-1982) depicting the ceremonial laying of the building's first cornerstone. I learned about the 1793 event on the website of Oglethorpe University, (re)founded by Thornwell Jacobs (1877-1956), the "father of the modern time capsule." The custom of burying a time capsule owes its origins to the Masons, who held rituals to lay cornerstones, often after placing memorabilia inside for later recovery. During his presidency, George Washington (1732-1799) performed the Masonic ritual over the Capitol's cornerstone and read the inscription on a silver plate that was laid in place with it. Exactly 200 years later, Masons from the Grand Lodge of the District of Columbia reenacted the entire ceremony - except that the original cornerstone has never been located. The Capitol has undergone extensive expansion, remodeling, and reconstruction, but neither the stone nor the identifying plate have been found despite extensive searches beginning with the building's Centennial in 1893. As I was finishing my research for this post I learned that Dan Brown's new novel - being released in September - is called The Lost Symbol, and it has been speculated that the cornerstone in question figures in the plot!