On August 20, 2008, the Thomas Jefferson Center for the Protection of Free Expression brought a time machine to the Community Chalkboard at the eastern end of the Downtown Mall. A crowd assembled was transported to the year 1828 to hear from James Monroe, the fifth President of the United States.
The Presidential time machine appears to operate once every August. In 2007, James Madison himself leapt from the past in order to give his view of history.
Madison and Monroe, lept back in time to discover they had left on their crocs and bling when they returned only to find they would lose the election the following years. :)