Related for Shevuot 6:5
וְאֵלּוּ דְבָרִים שֶׁאֵין נִשְׁבָּעִין עֲלֵיהֶן, הָעֲבָדִים, וְהַשְּׁטָרוֹת, וְהַקַּרְקָעוֹת, וְהַהֶקְדֵּשׁוֹת. אֵין בָּהֶן תַּשְׁלוּמֵי כֶפֶל וְלֹא תַשְׁלוּמֵי אַרְבָּעָה וַחֲמִשָּׁה. שׁוֹמֵר חִנָּם אֵינוֹ נִשְׁבָּע. נוֹשֵׂא שָׂכָר אֵינוֹ מְשַׁלֵּם. רַבִּי שִׁמְעוֹן אוֹמֵר, קָדָשִׁים שֶׁחַיָּב בְּאַחֲרָיוּתָן, נִשְׁבָּעִין עֲלֵיהֶן. וְשֶׁאֵינוֹ חַיָּב בְּאַחֲרָיוּתָן, אֵין נִשְׁבָּעִין עֲלֵיהֶם:
R. Meir says: There are things which are like land and which are not like land; and the sages do not concur with him. How so? (If one says:) "I gave you ten laden vines," and the other says: "They are only five," R. Meir requires an oath, and the sages say: Whatever is attached to the ground is like the ground. [Grapes awaiting harvest are the point of difference between the sages and R. Meir. According to R. Meir, grapes awaiting harvest are regarded as harvested, and according to the sages, they are not regarded as harvested. The halachah is in accordance with the sages. And this, only in respect to watchers (shomrim), but in respect to buying and selling and ona'ah (overcharging), and admitting part of the claim — in all of these they hold that what awaits harvesting is regarded as harvested. And this is the halachah.] An oath is taken only on something that can be measured or weighed. How so? (If one says:) "I gave you a house full (of produce)," or: "I gave you a pouch full (of money)," and the other says: "I don't know, but take what you put down," he is exempt (from an oath). If one says: "Until the ziz" [a beam of the upper story projecting from inside the house], and the other: "Until the window," he is liable. [The rule: One is never liable for a Torah mandated oath unless the claim is for something that can be measured, weighed, or counted, and there is admission of part of the measure, or weight, or count.]