The House of Arden by Edith Nesbit

Edred crept back to his stool, and took his corner of the marble-backed book of Dr. Watts with fingers that trembled. If you are inclined to despise him, consider that it was his first real adventure. Even in ordinary life, and in the time he naturally lived in, nothing particularly thrilling had ever happened to happen to him until he became Lord Arden and explored Arden Castle. And now he and Elfrida had not only discovered a disused house and a wonderful garret with chests in it, but had been clothed by mysterious pigeon noises in clothes belonging to another age. But, you will say, pigeon noises can't clothe you in anything, whatever it belongs to. Well, that was just what Edred told himself at the time. And yet it was certain that they did. This sort of thing it was that made the whole business so mysterious. Further, he and his sister had managed somehow to go back a hundred years. He knew this quite well, though he had no evidence but that one sheet of newspaper.

He felt it, as they say, in his bones. I don't know how it was, perhaps the air felt a hundred years younger. Shepherds and country people can tell the hour of night by the feel of the air. So perhaps very sensitive people can tell the century by much the same means. These, of course, would be the people to whom adventures in times past or present would be likely to happen. We must always consider what is likely, especially when we are reading stories about unusual things.