How do you sleep?

Have you ever been awake in bed, wondering when you're going to fall asleep?

I remember that as a teenager- but not really after, as I fall asleep so fast I've got a narcolepsy diagnosis. However, I'm pretty sure this came from learning to fall asleep anywhere I could.

We don't often ask: have people always needed mattresses to sleep well?

Consider these two groups of people:

• Tibetan Caravaneers in the early 20th century

• Kenyan Soldiers in the 1950s

If you had to guess, what sleeping positions would they have used?

Answers here.