The Japanese are masters of cat-napping. They are able to sleep anywhere, anytime. Their ability to squeeze in a quick nap is truly amazing. In Belgium I hardly ever see people sleeping in public, except for the occasional cat-nap on the train. But in Japan, I have seen people taking a nap in restaurants, while standing up on the train and even on the ground in the street!
If you want to see what the highest possible state of relaxation looks like, have a look at the post I wrote about school kids sleeping on the train.
But the most impressive example I saw of Japanese people being to sleep anywhere, anytime, is someone just taking a nap on the ground. And no, they were clearly not homeless people. Amazing!