As President Obama boarded Marine One on the South Lawn of the White House on Friday, he didn't return the salute of the Marine standing at the base of the stairs.

Obama realized it once he got into the helicopter, so he turned around and shook the Marine's hand. Here's video of the moment:

As happens with anything to do with the presidency, Obama's forgetfulness unleashed scrutiny and criticism.

But, perhaps, the more interesting thing to emerge from the coverage is a 2009 piece from The New York Times.

In it Carey Winfrey, the retired editor of Smithsonian magazine and a former Marine, talks about the history of the presidential salutes. He points out that his USMC instructor taught him never to salute without a hat or when he was out of uniform.

He goes on to say that the tradition of presidents — sans hat nor uniform — to return salutes started in 1981 with President Ronald Reagan. Winfrey explains:

"He had sought advice on the matter from Gen. Robert Barrow, commandant of the Marine Corps. According to John Kline, then Mr. Reagan's military aide and today a member of Congress from Minnesota, General Barrow told the president that as commander in chief he could salute anybody he wished. And so it began."

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