Today, many charts outline exactly how much matzah, maror, and wine must be eaten at he Seder. These shiurim, however, are significantly larger than what longstanding minhag requires.
For example, Rav Aharon Leib Shteinman, zt”l (a nephew of Rav Simcha Zelig of Brisk), said that Jews in Brisk used a becher that was 70 ml, which is 2.36 oz. Another gadol of the previous generation, Rav Shlomo Zalman Auerbach, zt”l, recounted that when Rav Avraham Chaim Naeh published his sefer on shiurim, Shiurei Tzion, the Jews of Yerushalayim were shocked at how machmir he was (Meged Givos Olam II, Darchei Hora’ah 12). Rav Chaim Naeh’s shiur for a revi’is is 86 grams, or 2.9 oz. (Interestingly, the number 86 is also the gematria of the word kos. The Chazon Ish’s shiur for a revi’is is 150 grams, which is the gematria of the words “kos hagun.”)
The following story sheds light on the opinion of Rav Moshe Feinstein, zt”l, regarding the shiur for daled kosos and Friday-night kiddush (which is mi’deOraisa). Rav Yaakov Moshe Shurkin, zt”l, once received a small kos as a gift. The cup held approximately 88 ml, which is 2.975 oz. The family was not sure if such a small kos could be used. Rav Shurkin’s brother-in-law, Rav Naftali Hirtz Kanterovitz (the son of Rav Yaakov Kanterovitz, zt”l), said he would take the cup to Rav Moshe. He returned the following day with the answer that it could, indeed, be used for kiddush; it was actually mehudar l’chatchilah. While this story is inconsistent with the view of Rav Moshe that is recorded in several books, it is a maiseh Rav, which is considered a superior source.
The Mishnah Berurah rules that one must use a larger shiur, but Rav Hillel Zacks, the Chafetz Chaim’s grandson, inherited the Chafetz Chaim’s kos, and it holds a smaller shiur. Perhaps an explanation for this discrepancy is that a larger shiur is required only as a hiddur mitzvah.
It is also cited in the Hagaddah of the Divrei Yoel that the shiur for a revi’is is 75 grams, or 2.54 oz.
Most bechers today are typically between 6-8 ounces. So in order to ensure that one fulfills this mitzvah k’mehadrin (it is better, for example, to drink the whole cup rather than just the majority), it may be advisable to use a smaller cup.
Dayan Aharon Dovid Dunner of London, England, asked the Steipler Gaon, zt”l, to show him the shiur of matzah that one is required to eat at the Seder. He brought him a whole matzah, a half a matzah, and a third of a matzah (all machine matzos). He also brought along some broken pieces as a joke.
But the Steipler picked up one of the broken pieces and said, “Aza shtickel b’erech hut der Chazon Ish mir gegebin tzu essen un er hut mir gezugt, ‘Oib du viltz kentz esen a bisel merr’ – A piece this size the Chazon Ish gave me to eat and said to me, ‘If you want, you can eat a little more.’”
Rav Dunner kept this piece of matzah, which is pictured here. It is about 10 centimeters long (approximately 3.9 inches).
It should also be noted that the Kehillas Yaakov (Pesachim 38) and Rav Avraham Tzvi Hersh Katzenellenbogen (in Sha’arei Rachamim, p. 19, #165, haga’ah 3) mention that Rav Chaim Volozhin was of the opinion that the kezayis required at the Seder is actually the size of an olive – around 3-4 cubic centimeters, or 1.5 x 1.5 inches.
There are opinions that one must eat more matzah. However mainstream minhag has always been to eat a smaller amount.
The Rambam (Hilchos Chametz U’Matzah 6:1) says that when a person has eaten a kezayis of matzah, he has fulfilled his obligation. The Netziv (Ha’emek Sheilah 53:4) infers that although a kezayis is the minimum amount a person must eat to fulfill his obligation, all the matzah one eats on Seder night is part of the mitzvah. However, it is important to know what is obligatory and what is extra – especially when there is a health concern.