Tatami as seating
The culture that developed in Japan from the Heian period (794–1185) onward, was not one that imitated that of the Asian continent. It was a culture unique to Japan. In this milieu, many pieces of literature such as The Pillow Book and Tale of the Genji came to be produced, as were picture scrolls that depicted these stories visually. These picture scrolls contain many depictions of tatami mats.
Take for example a scroll for the Tale of the Genji, a novel who’s hero is a playboy of the time. It contains a painting of women sitting on a thick, colorful ungenberi tatami mat, a style of mat with brocade hems. Meanwhile the Picture Scroll of Annual Events, which depicts events that take place in the court during the late Heian period, shows a tatami mat laid down outdoors, with people sitting on it and viewing a dance.
This shows us that tatami mats were used as portable seating by people of noble status. Incidentally, many of the characters that appear on the cards for the card game Hyakunin Isshu, whose subject matter is Heian period waka poems, are sitting on tatami mats. Hyakunin Isshu started to become popular in the 16th century. This suggests that the image of Heian period nobles sitting on tatami mats started around this time.
Tatami as bedding
The Diary of Lady Murasaki by Murasaki Shikibu, a popular writer of the time, is another picture scroll from this era, and it shows tatami being used as bedding. One of these scrolls depicts a tatami mat laid down in a bedroom, with a mattress known as a shitone spread out on top of it. A woman is sitting on top. Two women and a baby are on the tatami mat. This, and the size of the mat, tells us that it was not something used for sitting on, but was used as bedding instead.
As we can see, around the 12th century, tatami was used as appropriate; it was laid out where it was required and was used for as something on which to sit or sleep.
Tatami as flooring
With the coming of the age of the samurai in the 14th century, tatami mats came to be laid down to floor entire room. In addition, the thickness of the mats was adjusted to be the same height as the doorsill (the wooden rails used to hold fusuma sliding doors). Room sizes also came to be calculated so that there would be no gaps between the tatami mats and the doorsill or between the mats themselves. These are the origins of tatami’s use as a flooring material, which continues until this day.
From the Azuchi-Momoyama period, which began in the late 16th century, tatami rooms came to be loved by all the samurai, stimulating a thriving trade in tatami dealers, so much so that tatami quarters full of tatami shops also came into being. Later, in the middle of the Edo period (around the 17th century), tatami’s use as a floor covering expanded to include the houses of the commoners.
Tatami tradesmen making tatami appear in many of the ukiyo-e woodblock prints that depicted the lives of commoners during the Edo period. This shows that tatami shops were an everyday part of the lives of this class. A type of building known as nagaya existed in the towns and cities of the Edo period. Nagaya were a kind of collective housing used by the commoners. It appears that people moving into these houses would bring their own tatami mats with them and start living in the building once the mats had been laid down. Tatami mats came to be a possession that it was impossible to live without, so people would take their tatami mats with them when moving to another nagaya.