Contemporary Masonic practice included the laying of an inscribed metal plate along with a cornerstone. Caleb Bentley, a Quaker clockmaker and silversmith who lived in Georgetown not far from Suter's Fountain Inn, where the commissioners held their meetings, made the silver plate for the Capitol ceremony.
The newspaper invitation announcing the cornerstone ceremony was directed to the Masonic fraternity:
The Capitol is in progression—the southeast is yet kept vacant that [the] cornerstone is to be laid with the assistance of the brotherhood [on] the 18th Inst. Those of the craft however dispersed are requested to join the work. The solemnity is expected to equal the occasion.
The ceremony proceedings were reported in an article in The Columbia Mirror and Alexandria Gazette, which remains the only known eyewitness account of the event. Activities began at 10:00 a.m. with the appearance of President Washington and his entourage on the south bank of the Potomac River. Crossing the river with the president was a company of volunteer artillery from Alexandria. The procession joined Masonic lodges from Maryland and Virginia, and all marched two abreast, "with music playing, drums beating, colors flying, and spectators rejoicing," to the site of the Capitol about a mile and a half away. There the procession reformed and Washington, flanked by Joseph Clark (the Grand Master) and Dr. E. C. Dick (the master of the Virginia lodge), stood to the east of a "huge stone" while the others formed a circle west of it. Soon, the engraved plate was delivered and the inscription read:
This South East corner stone, of the Capitol of the United States of America in the City of Washington, was laid on the 18th day of September, in the thirteenth year of American Independence, in the first year of the second term of the Presidency of George Washington, whose virtues in the civil administration of his country have been as conspicuous and beneficial, as his Military valor and prudence have been useful in establishing her liberties, and in the year of Masonry 5793, by the Grand Lodge of Maryland, several lodges under its jurisdiction, and Lodge 22, from Alexandria, Virginia.
Thomas Johnson, David Stuart and Daniel Carroll, Commissioners
Joseph Clark, R. W. G. M.—P. T.
James Hoban and Stephan Hallate, Architects
Collen Williamson, M. Mason
The plate was handed to Washington, who stepped down into the foundation trench, laid the plate on the ground, and lowered the cornerstone onto it. With the president were Joseph Clark and three "worshipful masters" bearing the corn, wine, and oil used to consecrate the stone. Chanting accompanied Washington’s ascent from the trench. Clark gave a speech punctuated by numerous volleys from the artillery. Following the formal exercises, a 500 pound ox was barbequed and those in attendance "generally partook, with every abundance of other recreation." By dark, the festivities had ended.
In 1991, a search for the Capitol Cornerstone was conducted including use of a metal detector to locate the engraved plate—it was not found. The location may be under the south east corner of what is today National Statuary Hall.