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Regarding the kezayit measurement, there is one other point worth mentioning. Everyone knows that one is required to eat a kezayit of maror at the Seder. Nevertheless, the practice of the Ropshitz hasidim used to be precisely the opposite, as they were careful not to eat a kezayit of maror. This strange practice goes back to the founder of the Ropshitz dynasty, R. Naphtali Zvi Horowitz (1760-1827). (I don’t know if the practice continues today.) Not only is the lack of a kezayit problematic, but there is the other issue regarding whether one can even say a blessing on the maror with less than a kezayit.

R. Aryeh Zvi Frommer deals with Ropshitz practice, and also mentions that he heard that R. Shalom of Belz and R. Ezekiel of Shinova also told people to eat less than a kezayit of maror and to make the blessing on it.[25] R. Frommer attempts to justify this practice halakhically, and he states explicitly that he is doing so in order that the actions of these hasidic masters not be in contradiction to the Mishnah, Pesahim 2:6, the meaning of which appears to be that a kezayit is the minimum amount required for maror.[26] He also notes that he wants to justify the practice of “most of Israel” who use horseradish for maror and also do not eat a kezayit. His justification is only of eating less than a kezayit of horseradish, so it does not seem that this will be of any help with regard to the view of the Ropshitzer, as his avoidance of a kezayit of maror apparently applied to all types of maror, even lettuce.

Many people probably remember their grandparents telling them that in Europe they used horseradish for maror, but that unlike today there was no concept of being careful to eat a kezayit. If you had any doubts about what your grandparents reported, R. Frommer tells us the exact same thing. Are we to say that most Jews in Europe did not fulfill the mitzvah of maror? This is a conclusion that no rabbi wants to reach, and that is why R. Frommer is motivated to find some justification for the practice.

R. Frommer was obviously concerned that what he wrote would be regarded as too radical. Thus, on the very last page of the book, where one finds the corrections, he stressed that his words were only a limud zekhut because most people do not eat a kezayit, but le-khathilah one cannot rule this way.

There is no need for me to go into this matter in any detail, as it has been comprehensively analyzed in a wonderful article by Levi Cooper.[28] I would just like to call attention to some sources not mentioned by Cooper.

1. R. Mordechai Shabetai Eisenberger, Berurei Halakhot (Netanya, 2006), no. 51, offers a halakhic justification for the Ropshitzer, and claims that it is only applicable to horseradish.

2. The following story, quoting R. Aaron Rokeach, the Belzer Rebbe, appears in Aharon Pollak, ed., Beito Na’avah Kodesh (2007), vol. 2, p. 482:

3. The following story, that R. Joel Teitelbaum of Satmar refused to follow his father-in-law’s practice of eating less than a kezayit of maror, appears in Aharon Perlow, Otzroteihem shel Tzadikim al ha-Torah ve-ha-Moadim (2006 edition), p. 323, quoting Moshian shel Yisrael, vol. 4, p. 17:

4. Matityahu Gutman, Belz (Tel Aviv, 1912), p. 31, states: