Rav Isser Zalman Meltzer

Rav Isser Zalman Meltzer (1870 – November 17, 1953) was born in the city of Mir, Poland. At the age of 10 he learned at the Mir Yeshiva. By the age of 14 he went to learn in Volozhin yeshiva under the Netziv and Rav Chaim Soloveitchik, where he remained for seven years. He went on to become a maggid shiur in the Slabodka Yeshiva and later the Rosh Yeshiva to Chevron in Eretz Yisroel. He left behind many talmidim including the postwar architects of Torah in America, Rav Aharon Kotler, Rav Yaakov Kamenetsky, Rav Yitzchok Hutner, and Rav Yaakov Yitzchok Ruderman.

Rav Isser Zalman once said that he was able to discern if a cup had been ritually immersed or not. He would try to write the name of Hashem on the side of the cup, and if the letters became unclear it was a sign that the cup had not been immersed.