The United States Constitution gives the President the option of either swearing the oath or affirming it. Hoover is often listed as having used "affirm" due to being a Quaker, but the newsreel taken of the ceremony indicates that the words used were "solemnly swear."Franklin Pierce was the only president known to use the word "affirm" rather than "swear."
In administering the oath, Taft erroneously recited the phrase "preserve, protect and defend" as "preserve, maintain and defend". Helen Terwilliger, a 13-year old eighth-grade student in Walden, New York, caught the error and wrote to the Chief Justice to tell him. Taft conceded that he had made an error, attributing it to "the defect of an old man's memory", but asserted that he had made a different error, misquoting the words as "preserve, maintain and protect". Terwilliger did not back down from her claim; the Fox Film Corporation, Pathe News and Paramount News, the companies who had prepared newsreels of the inauguration, examined their recordings and jointly confirmed Terwilliger's account.