I’ve seen mention of the “Water Level Route” which followed a much easier route so as to give a smoother ride.
I’ve never slept on a steam-hauled train, or on a train on a route as severe as US and Canadian trans-continental routes. I’ve experienced British sleepers, which are diesel hauled and pretty comfortable (apart from Station tannoys at Crewe and Glasgow). I’ve experienced a Russian sleeper once, which was... all a bit Russian.
I’d be interested in hearing about experiences of American sleepers, old and new?