Twenty-fifth Amendment to the United States Constitution
On June 29, 2002, President George W. Bush became the first President to officially invoke Section 3.  He needed a colonoscopy, a test of the colon, and would be getting anesthesia.  He formally gave power to his Vice President, Dick Cheney, using the rules that the 25th Amendment set out.  Unlike Reagan, he specifically said he was using Section 3 of the 25th Amendment in his letter to the President pro tempore and the Speaker of the House.  After about two hours, Bush was awake and took back the Presidency.