Why "sit zen" when its a sauna?

The Zafu Zafu is a secret to its shape and unique firmness is the reason Zafu is used since ancient times in temple Zen temples.The Zafu is a firm cushion with a plump zabuton and firm bread, and the Zafu sits on your hips when you set up the zabuton, giving you support to keep your spine correct. The ZAF SAUNA was tuned to the sauna with its effectiveness.By supporting your back muscles in the sauna, you can effectively soak heat waves and breathe easily.

Why do I think it is a sauna, but why "cushion?

Purchasing book sauna roots are believed to be in Buddhism.In the sutra of the "Buddhist Washers of the Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist Buddhist This means sauna was used in temples instead of the main temple, and the connection between Zazen and Sauna was actually very close.