Kotatsu: The Japanese heating table

I've been meaning to look into what these were for a while now, I've seen them so much in anime with many characters talking about and around them yet I've never bothered to remember what they are. I'm talking about the Kotatsu.

Kotatsu: a light blanket (Shitagake) is covered by a heavier blanket (Kogatsu-gake) under the tabletop

The Kotatsu is a Japanese table that has heating underneath it (mainly electric these days but it used to be coal), sealed from the outside with a blanket/futon insulation running around the edge. Obviously the upper half of your body would still be exposed but the theory was that the heat would travel up from the bottom of your robe to the top, basically creating a warm current. I don't know if this actually worked or not but one thing's for certain, it sounds like the Japanese have it rough when it comes to heating. Apparently there are few modern Japanese apartments that have central heating as well as air conditioning so usually the tenants have to provide it themselves which isn't as effective. Indeed this clearly makes the Kotatsu an important part of the house, one where the family gather round for dinner, or watch telly.

Top one is the more mobile, electric Kotatsu or Oki-gotatsu and the one underneath is the stationary Charcoal Kotatsu or Hori-gotatsu

 It being something for people to gather round makes it a focal location for conversation in many anime.

Apparantly there's a saying or belief that if you sleep under a Kotatsu you'll catch a cold

I'd love to have one at my place, not just for the sake of having something Japanese in the house but because I reckon it looks genuinely really comfortable. I'll definitely have to get one at some point in my life, especially if I get a cat

Pets have taken advantage of the Kotatsu, it must be amazing to be able to fit under one

Here are the sources for my information:

TV Tropes
The Kotatsu: a different way of thinking about Tables
Kotatsu: The Heated Small Space Desktop
The Cold and the Kotatsu
Kotatsu wikipedia