It is a fact that contemplation can become so deep and the personality so lost for the time being that when the period of practice is over the meditator may need a little time to accustom himself to his surroundings, just as any ordinary person who awakens from a very deep sleep may need several seconds to become conscious of his physical surroundings. In this half-absentminded state he may even fail to recognize someone else in the room. This happened once to the famous professor D.T. Suzuki, the great Zen teacher, after we had been sitting together in a private meditation in his study. Although the period was not at all long, when the silence was broken and he began to speak, he addressed the question to me, asking, "Who are you?" Of course after some seconds he came back into full consciousness and remembered.
-- Notebooks Category 23: Advanced Contemplation > Chapter 7: Contemplative Stillness > # 334