I think he told me that for forty years he slept only an hour and a half during the night and that in the beginning this was his greatest penitential trial, to conquer sleep, and that to do this he was always either on his knees or standing. When he did sleep, he did so sitting up, with his head resting on a little log nailed to the wall. He could not have stretched out even if he wanted to, because his cell – as is known – was no larger than four and a half feet. However hot or rainy the weather was in all those years, he never put up his cowl; he wore nothing on his feet, nor did he wear any clothes other than a course serge habit with nothing else to cover the body – that was as tight as could be, and a short mantle over it made of the same material. He told me that when it was terribly cold he took the mantle off and left the door and little window of his cell opened so that afterward by putting the mantle on again and closing the door he was able to appease the body by the warmth that came from more covering. Eating every third day was a very common practice with him, and he told me when I showed surprise that it was easily possible for anyone who got used to doing so.
– St. Teresa of Avila, The Book of Her Life.