Supreme Court in Cramer v. United States, quoted in Crane, Paul T.; Pearlstein, Deborah. "Interpretation: Treason Clause". National Constitution Center.
Specifically Edward II, Richard II, Henry VI, Edward V, and Charles I. See Edward Coke's Institutes of the Lawes of England, Third Part, chapter 1: "He that declareth by overt act to depose the king, is a sufficient overt act to prove, that he compasseth and imagineth the death of the king."
