While not used much in modern times, I've recently become a fan of wearing a nightcap at night.

According to Wikipedia, they were common in northern Europe before central heating became popular.

In my own case, in recent times I've been sporting a shorter haircut and find that it can be cool at night to have less hair up on top. Our house does not have central heating per se, but we do have a wood stove to heat the house in winter. However, while asleep, the temperature slowly drops as the wood stove runs out of fuel.

When I first thought of the nightcap last year, I was optimistic that finding a simple hat to wear at night would be easy. This wasn't quite the case because I was searching for a cheap fleece hat. Finally I settled on a simple wool knit toque that I picked up at the dollar store/¥100 store.

I was amazed at how quickly I became drowsy when wearing the nightcap and at how well I slept. I also found the nightcap had the added benefit that, because it was loose and slid down partly over my face while sleeping, the nightcap also blocked light as morning slowly started emerging.

Should your dwelling be slightly cool at night, and should your noggin be slightly cold, may I recommend a nightcap? Happy dreams.