We've been covering the Constitution in most classes recently and in 2301 read through the part in Article 6 that mandates that officials be "bound by Oath or Affirmation, to support this Constitution." I used this to comment on what an oath is as opposed to an affirmation.
Just now I stumbled across mention of Franklin Pierce's inauguration, which took place soon after his young son was killed in a train accident. According to the story he refused to swear an oath on the Bible at the ceremony and is the only president who affirmed rather than swore his loyalty to the Constitution.
