Talmud for Eruvin 8:6
בּוֹר שֶׁבֵּין שְׁתֵּי חֲצֵרוֹת, אֵין מְמַלְּאִין מִמֶּנּוּ בְשַׁבָּת, אֶלָּא אִם כֵּן עָשׂוּ לוֹ מְחִצָּה גָבוֹהַּ עֲשָׂרָה טְפָחִים בֵּין מִלְמַעְלָה, בֵּין מִלְּמַטָּה, בֵּין מִתּוֹךְ אֹגְנוֹ. רַבָּן שִׁמְעוֹן בֶּן גַּמְלִיאֵל אוֹמֵר, בֵּית שַׁמַּאי אוֹמְרִים, מִלְּמַטָּה. וּבֵית הִלֵּל אוֹמְרִים, מִלְמָעְלָה. אָמַר רַבִּי יְהוּדָה, לֹא תְהֵא מְחִצָּה גְדוֹלָה מִן הַכֹּתֶל שֶׁבֵּינֵיהֶם:
A hole between two courtyards, [half in one and half in the other] — it is forbidden to fill up from it on Shabbath, [for (in doing so) one fills up from his neighbor's domain; and this is forbidden if the courtyards had not been joined by an eruv], unless they make for it a partition ten tefachim high, whether above [i.e., nine tefachim of the partition above the water and one tefach submerged in it], or below [i.e., nine tefachim submerged in it and one tefach visible above], or from the midst of its cavity, [even though the partition does not touch the water at all, this being a lenient ruling of the sages vis-à-vis water, (the sages) saying that we perceive the partition as extending downwards. This, so long as it is in the midst of the cavity of the hole, so that it is perceived as a partition.] Beth Shammai say: below. Beth Hillel say: above. R. Yehudah said: The partition should not be greater than the wall between them! [i.e., (It should not be more effective) than the wall itself that separates the courtyards and runs over the hole, even though it does not descend into its cavity (i.e., the partition is superfluous.) The halachah is not in accordance with R. Yehudah.]