From Rabbi Aryeh Kaplan's “Meditation and the Kabbalah” (Jason Aronson or Samuel Weiser editions).
Rabbi Shimon Bar Yochai
Among the disciples of Rabbi Akiba, the most prominent mystic was Rabbi Shimon bar Yochai, best known as the author of the Zohar (“Book of Splendor”). Although Rabbi Shimon obviously received a good part of the mystical tradition from Rabbi Akiba, he was not considered his prime disciple in this area. This honor was reserved for a colleague of Rabbi Shimon, Rabbi Chananya ben Chanikai (Talmud: Chagigah 14b).
With Rabbi Shimon, however, a new school was developed. The account of Rabbi Shimon's thirteen-year stay in a cave with his son [Rabbi Elazar], hiding from the Roman officials, is well known. Rabbi Shimon had denounced the Romans and had been sentenced to death, barely escaping to this cave. During his stay there, Rabbi Shimon engaged in esoteric meditations and prayers, until he was worthy of a mystical revelation of the prophet Elijah. Elijah taught him the deepest of mysteries, which were later to make up the main body of the Zohar.
Rabbi Shimon left the cave around the year 138 c.e., shortly after the death of Hadrian, and established a new school of mysticism. This school continued after his death, and some seventy years later, his disciples wrote down his main teachings, forming the main body of the Zohar. These later writings were distinguished from the "first Mishnah , which was written by Rabbi Shimon himself.
Rabbi Shimon's school survived for many years, during which minor additions were made to the Zoharic literature. For over a thousand years, this body of literature consisted of volumes of notes, restricted to a very small secret society. With the final disbandment of this society, the manuscripts were hidden in a vault, and were not uncovered until the thirteenth century. They finally came to the hands of Rabbi Moshe de Leon, one of the most prominent Kabbalists of that time, and he finally edited and published them in the 1290's.