Excerpts of the President's News Conference
An inquiry about the authority of the President to pardon. I don't know that there has been any direct decision of the courts about that. There are quite a number of opinions of the Attorney General on it from time to time. There are different kinds of contempt. This, I think, was a proceeding under a criminal contempt, which perhaps would make it more plain that the President would have the power of pardon. If it were a civil contempt, then perhaps the President wouldn't have. I spoke of it when it first came up, in relation to my experience as Governor of Massachusetts when there was, it was my impression, no authority on the part of the Governor to pardon in contempt cases. That is an action of the court for the purpose of giving the court authority to administer its business. A person may be called before the court to testify. If he refuses to testify then the court has authority to imprison him until he does. Now that isn't a crime in any way, and that he should be kept in confinement until he testifies, or if he doesn't come to send the sheriff after him and bring him. That is not on the criminal side of jurisdiction at all, but if a criminal contempt is committed, which I understand was claimed in this case, then it brings it on the other side of the court.
Source: "The Talkative President: The Off-the-Record Press Conferences of Calvin Coolidge". eds. Howard H. Quint & Robert H. Ferrell. The University Massachusetts Press. 1964.
Calvin Coolidge, Excerpts of the President's News Conference Online by Gerhard Peters and John T. Woolley, The American Presidency Project https://www.presidency.ucsb.edu/node/349019