You can find the original text at this Sado Nyumon.

How to Walk

You shouldn’t step on thresholds or edges of the tatami mats.

One tatami mat is about six feet long and half a tatami mat is three feet long, so walk planning on advancing forward at only a foot’s length. When you are not carrying anything, both hands should hang naturally in front. The position of the eyes is slightly lowered, rather than straight ahead.
Entering the tea room, enter with your left foot (first).

Walk as one tatami mat is about five steps (natural steps). Settling the hips, and putting strength into the lower abdomen, stand up straight. Pull the chin to the degree (as when) you look forward. As for the hands, if you are a man, the tips of your thumb and index finger meet, making a little circle. Then lower them to your side. If you are a woman, arranging your fingers naturally, lower them to the front. With each step, you should walk like you are slightly raising the tips of your toes and do not seperate the heels from the tatami.
Entering the tea room, enter with the right foot. Leaving, leave with the left foot.

You should aim to walk one tatami with six steps. Also, so that you interpose the center line of the tatami, walk both sides straightly. Shift your balance from one foot to the other. For example, when you step forward with your right foot, leave your balance in your left foot with the tip of the toe to the right foot you stepped forward with a little unsteady. Gradually shift your balance to the right foot as the right foot falls behind. At the same time, the left heel becomes unsteady. Next, the right foot holds your balance and the left foot advances. When the right foot passes right beside (your left), the tips of your feet appear level for a moment. As you continue forward and leave, the tip of the left toe becomes unsteady. If you repeat this movement, you can walk in a smooth manner.
Entering the tea room, enter with the foot (closest) to the pillar (supporting the wall). When you leave, there is no established rule.
NB: According to the matter of entering with the foot closest to the pillar, it is for the sake of turning your upper body in the direction of the guests. Therefore, according to the tea room, which foot–right or left–you enter with changes.