The Measure of Establishing a Meal

What is the measure of establishing a meal, for which one must bless on mezonot, perform hand washing, say the blessing on bread, and Birkat Hamazon?

One should not eat more than a volume of 216 cc (the measure of 4 eggs, with each egg being 54 cc), which is slightly more than a disposable cup of 180 cc. (Other items that accompany the bread do not combine with this measure). Nevertheless, one does not bless Birkat Hamazon until eating a measure of 800 cc, which is approximately 3/4 of a milk bag. (Other items that accompany the bread do combine with this measure).

Shulchan Aruch, Orach Chaim, Siman 168, Seif 6: "Pat haba'ah bekisnin, one blesses on it: 'Borei minei mezonot', and afterwards: 'Bracha achat me'ein shalosh'; and if one ate from it a measure that others usually establish as a meal, even if he himself was not satisfied, he blesses on it: 'Hamotzi' and Birkat Hamazon.

What is this measure? Mishnah Berurah, Siman 168, SK 24: "Regarding eruv techumin in Siman 368, it states that the measure of a meal is 3 or 4 eggs. And several later authorities write that this is also considered the measure of establishing a meal here, but several later authorities, including the Gra, disagree and hold that one blesses 'Hamotzi' and Birkat Hamazon only at the measure of an established meal, which is of morning and evening, as written in Beit Yosef in the name of Shibolei HaLeket, and so I found in Eshkol, which proves that he holds so, and so more inclines the language of the Shulchan Aruch. Nevertheless, initially, it is good to be concerned with the opinion of those who are stringent not to eat 4 eggs, and certainly if it is a matter that is doubtful by law if it is pat haba'ah bekisnin.

Thus, the Mishnah Berurah ruled not to eat more than 4 eggs, but one does not bless Birkat Hamazon until the measure of a morning and evening meal.

The Shulchan Aruch HaRav writes that this measure corresponds to an omer per person for two meals, which is the measure of 3 eggs and 1/5 of an egg, which descended to Israel in the manna, and thus the measure of one meal is 2 1/2 eggs. And in the Gemara, Eruvin, page 83, side 2, it says: "One who eats more than this is a glutton, and one who eats less than this in a meal has digestive issues."

In practice, our teacher, the Gaon Rabbi Amram Fried, shlita, ruled that 800 cc appears to be the measure of establishing a meal in our days.

And what I wrote that for the measure of 800 cc the accompaniments are combined, and for 216 they are not combined, so it is explained in Shaar HaTzion, Siman 168, SK 19.