The Buddha said to his monks: "It is the rainy season and I wish to live in solitude for these three months. I would like my only visitor to be the one who brings me food."
At the end of three months, he said: "Monks, if those of other faiths were to ask you,
"What meditation did the Buddha practice during the rains?' You should say, 'He spent the rains practicing the meditation of mindfulness on the in and the out breath.' It was in this way, monks, that mindfully I breathed in and mindfully I breathed out. When breathing a long breath, I knew that it was long; and when breathing it out I knew 'I breathe out a long breath.' The same with the short breath, knowing it to be entering and knowing it to be leaving. In mindfulness I was conscious of the entire process.
"In this way also, I practiced contemplation on the body. When standing, I was aware that I was standing; when sitting, there was total knowledge of sitting; and when lying down, the full experience of lying down. By experiencing each moment, my mind clung no more to the world.
"The mindfulness of in and out breathing, of body contemplation, of keeping consciousness of the moment, is a noble occupation and a sublime way, leading to independence of mind and to wisdom."
From The Dhammapada