Mishnah 2 in the ninth chapter of Menachos continues to discuss the measuring vessels used in the Beis HaMikdash for measuring liquids. The Mishnah opens by stating: "Sheva midos shel lach hayu bamikdash" - seven different sizes of measuring vessels for liquids were used in the Mikdash.
The count of seven is based on a tradition that there were specifically seven different sizes. Because of this, the Mishnah lists even vessels that were no longer needed in practice, but which were required in order to complete the count of seven.
The measure of the hin:
The hin is the largest of them, equal to twelve lugin - roughly six liters. This measure was not in use in the time of the Mishnah. In the time of the Mishkan, Moshe Rabbeinu used it to make the anointing oil with which the Mishkan and its vessels were anointed at their dedication. In later generations, during the first Beis HaMikdash, that oil was used to anoint the kings of the house of David, to anoint the Kohen Gadol, and to anoint the kohen anointed for war - the kohen who accompanies those going out to battle. During the second Beis HaMikdash the anointing oil no longer existed.
The making of the anointing oil was therefore a one time event, since the Torah forbids producing it anew. Even so, the tradition was that a hin measuring vessel had remained in the Mikdash ever since, and because of the tradition of seven measures it continued to be counted.
The seven measures in the Mishnah:
Hin - twelve lugin.
Half a hin - six lugin.
A third of a hin - four lugin.
A quarter of a hin - three lugin.
A full log.
Half a log.
A quarter of a log.
What each of these measures was used for will be listed in the next Mishnah; the point here is the count itself - seven measures in all.
The view of Rabbi Eliezer ben Tzadok:
Rabbi Eliezer ben Tzadok did not have this tradition, and in his view there is no need for seven separate sizes; one can manage with far fewer measures, and even with a single vessel. He therefore says: "Shenasos hayu bahin" - there was one hin measuring vessel there, marked with lines showing how far to fill it for each offering:
"Ad kan lapar" - the bull requires half a hin of wine and oil.
"Ad kan la'ayil" - the ram requires a third of a hin.
"Ad kan lakeves" - the lamb requires a quarter of a hin.
According to Rav, all seven quantities listed in the Mishnah were marked on that one large vessel with different markings. According to Tosafos, only the hin and its fractions were measured on the hin vessel, while the log measures were in a separate vessel, since the log is far smaller and it is difficult to measure such a small amount accurately in a large vessel.
The view of Rabbi Shimon:
Rabbi Shimon holds that there was indeed a tradition of seven measures, but in his opinion there was no hin in the Temple at all, since it had no use, and therefore a different seventh measure must be added in its place. The language of the Mishnah: "Lo hayah sham hin, vechi mah hayah hin meshamesh?" - a rhetorical question: there is no offering and no meal offering that requires a full hin measure.
"Ela midah yeseirah shel log vachetzi haysah sham, shebah hayah moded leminchas kohen gadol" - with this vessel they would measure the oil for the chavitin meal offering of the Kohen Gadol. This meal offering requires three lugin, but half of it is brought in the morning and half in the evening, as the Mishnah says: "Log vachetzi baboker velog vachetzi bein ha'arbayim". Therefore there was a measuring vessel there the size of a log and a half.
The halachah:
Rabbi Shimon's view is somewhat difficult to understand, since the Gemara ultimately says that each of the twelve loaves of the chavitin meal offering has its own separate portion of oil, a quarter of a log for each loaf. True, six loaves together come to a log and a half, but since the measuring is done for each loaf on its own, it is hard to understand why a measure of a log and a half was needed. In any case, this was Rabbi Shimon's view.
The halachah was decided in accordance with the first Tanna: there were seven liquid measures in the Temple, and one of them is the hin.