[arien]

I've been on a fair amount of sleeper trains and the Caledonian has been the most comfortable so far.

For the opposite, the most uncomfortable one to sleep in was the Hong Kong to Shanghai one. I paid extra for the Deluxe option, can't even imagine how hard the bed would have been on the lower classes. Still, was a pretty cool journey.

[nhf]

I think that's just an (northeast) Asian bed thing. Preferences trend firm for mattresses and you can see this in traditional or luxury places that don't cater to Westerners. The most deluxe ryokans in Japan still have relatively thin mats on the floor, business hotels in China and Japan often have former mattresses, and so on.

[buckminster]

I took a 44 hour train from Delhi to Bombay. The "bed" was a plastic-covered sheet of wood, like a cheap kitchen worktop. That was uncomfortable. I think it was standard class.