Responsa for Bava Batra 71:11

הנהו עיזי דאכלו חושלא בנהרדעא אתא מרי חושלא תפסינהו והוה קא טעין טובא אמר אבוה דשמואל יכול לטעון עד כדי דמיהן דאי בעי אמר לקוחות הן בידי והאמר ר"ל הגודרות אין להן חזקה שאני עיזי דמסירה לרועה

Some goats [went into a field] in Nehardea [and] ate some peeled barley [which they found there]. The owner of the barley went and seized them, and made a heavy claim on the owner of the goats.<span class="x" onmousemove="('comment',' I.e., he asserted that the goats had eaten barley to a much greater value than their own. ');">¹⁹</span> The father of Samuel said: He can claim up to the value of the goats, because if he likes he can plead that the goats themselves are his by purchase.<span class="x" onmousemove="('comment',' I.e., if he asserted that the goats belonged to him, his plea would be valid (in default of rebutting evidence). Hence, in default of further evidence on either side, he can claim compensation up to the value of the goats. ');">²⁰</span>

Maharach Or Zarua Responsa