Monday evening is the start of Lag b’Omer. This special day commemorates a number of important events in the history of the Jewish people. One of these is the revelation of Jewish mystical teachings by Rabbi Shimon bar Yochai (or Rashbi), who had fled from the Romans and spent a total of 13 years hiding in a cave with his son. As is well-known, the teachings that he revealed would later be expanded upon and compiled into the Zohar, the primary textbook of Kabbalah. What isn’t as well-known is that there are several other ancient texts attributed to Rashbi. Perhaps the most enigmatic is Nistarot d’Rabbi Shimon bar Yochai, the “concealed matters” or “secrets” of Rashbi.