The size of a tatami mat (90 x180 cm) is not only an acre, but also the dimensions for the altitude of the space. This makes the space in the tatami room so elegant and simple.
Roland Barthes wrote in his book L’Empire des signes:
When I talked with setdesigner Masako Ito about dimensions, she said that she takes the size of the tatami as a basic. But she also asked the size of the tallest actor/actress. Than she changes the proportions of the whole scene to a comfortable size of the tallest man/woman.