Pope Benedict and President Bush pray together "for the family, as an institution"

The Prayer of the Pope and the President, Reuters. April 16, 2008:

WASHINGTON (Reuters) - Pope Benedict and U.S. President George W. Bush and his wife Laura prayed together in the White House on Wednesday, the Vatican said.

Vatican spokesman Rev. Federico Lombardi said that the "brief prayer" took place after the pope and Bush had finished their private talks in the Oval Office and Laura Bush joined them.

"There was a brief prayer for the family (as an institution)," Lombardi said.

Bush is a Methodist. Both he and the Roman Catholic pope have said that the traditional family, based on the marriage of a man and a woman, is under threat.

I wonder how many other Popes and U.S. Presidents have prayed together?