Mrs. Pond, Clara, Clemens and Major Pond. Crossing the Rockies. The Great Northern. August 9.
Mark Twain Archive, Elmira College courtesy of Kevin Mac Donnell, Austin, Texas.

Major Pond either was mistaken about the location, "crossing the Rockies", or he was unaware that these were the Cascades they were crossing. Twain remarked in his journal that they had stopped a short distance from Wellington and threw rocks down the precipice. Embro is the most likely spot for this.