Yahrtzeit of Rabbi Chaim Vital (1543-1620), the primary disciple of the famed kabbalist, the Arizal. Rabbi Vital was born in Tzfat, studying under the great Rabbi Moshe Alshech and Rabbi Moshe Cordevero. The Arizal, who died at age 38, taught Rabbi Vital for only two years. But Rabbi Vital diligently transcribed the Arizal's teachings, which have served as the basis for all subsequent study of kabbalah. Rabbi Vital also authored his own kabbalistic work, Aitz Chaim.
Nissan 30 is also the yahrtzeit of Rabbi Yaakov Emden (1698-1776), known by the acronym Yavetz. Born in Germany, Rabbi Emden was the son of a great rabbi known as the Chacham Tzvi. Emden was a controversial figure who relentlessly opposed the Shabbatai Tzvi messianic movement, and accused the great Rabbi Yonason Eibshutz of being a follower of that movement. Shabbatai Tzvi was a dangerous character who had declared himself the Jewish messiah, and predicted that 1666 would be the year of Israel's redemption. When the prediction did not come true, Shabbatai Tzvi converted to Islam, leaving behind a distraught Jewish community. Rabbi Emden's scholarship is preserved in a set of responsa, She'eilat Yavetz.