President Donald Trump, when taking his most recent oath of office, did not appear to place his left hand on either of the Bibles brought to the swearing-in ceremony in the Capitol Rotunda on Monday.

The tradition of using a Bible during the swearing-in goes back to the very first inauguration, but not all Presidents have used one.

Some presidents did not use a Bible to take the oath of office, including Theodore Roosevelt, who did not use anything when he was sworn into office in 1901, and John Quincy Adams, who chose a legal book for his 1825 swearing-in, to signify his responsibility to uphold the U.S. constitutional law.