The following is an excerpt from the Indianapolis Examiner (I can't believe I missed this one!); click the above link to read the full article:
Listen carefully for ghostly chuckles during your next visit to Les Invalides. If you hear them, don’t worry - it’s merely Napoleon smirking at the continuing fallout from his 1798 Egyptian Campaign.
In 1799, soldiers constructing Fort Julian at a port city called Rosetta (now called Rashid) pulled a large black stone, almost 4 feet tall, 28 inches wide, 11 inches thick and weighing approximately 1,700 pounds, out of the Nile delta muck. Imagine their shock at seeing the inscriptions after it was cleaned off.
The article includes pictures and many links to other resources on the topic.