Eruvin 72A

וחד אמר: ביין דכולי עלמא לא פליגי דבעינן תרתי, כי פליגי בפת.

And one said: In the case of wine, everyone agrees that two are required, both a merging of alleyways and a joining of courtyards. When they disagree is in a case where an eiruv was established with bread: R' Meir maintains that both a merging of alleyways and a joining of courtyards are required, whereas the Rabbis say that one is sufficient.

מיתיבי: וחכמים אומרים או מערבין או משתתפין. מאי לאו: או מערבין בחצר בפת, או משתתפין במבוי ביין.

The Talmud raises an objection from the baraita itself. And the Rabbis say: One may either establish an eiruv or a merging of alleyways. What, does it not mean that one either establishes an eiruv in the courtyard with bread or a merging in the alleyway with wine, which indicates that they also disagreed in a case where a merging of alleyways was established with wine?

אמר רב גידל אמר רב, הכי קאמר: או מערבין בחצר בפת ⁠— ומותרין כאן וכאן, או משתתפין במבוי בפת ⁠— ומותרין כאן וכאן.

Rav Giddel said that Rav said that the Rabbis were saying as follows: One may either establish an eiruv in the courtyard with bread, and it would be rendered permitted to carry both here, in the courtyard, and there, in the alleyway, or one may establish a merging of alleyways in the alleyway with bread, and it would be rendered permitted to carry both here, in the courtyard, and there, in the alleyway.

אמר רב יהודה אמר רב: הלכה כרבי מאיר. ורב הונא אמר: מנהג כרבי מאיר. ורבי יוחנן אמר: נהגו העם כרבי מאיר.

Rav Yehuda said that Rav said: The halakha is in accordance with the opinion of R' Meir. And Rav Huna said: No clear halakhic ruling was issued in his favor, but the custom is in accordance with the opinion of R' Meir. Therefore, if someone asks, he should be instructed to act accordingly. And R' Yoḥanan said: It is not even a custom established by the rabbis. Rather, the people were accustomed to act in accordance with the opinion of R' Meir, and we do not tell them they have acted inappropriately.