Mishnayos Peah Perek 2 Mishnah 6

It happened that Rabbi Shimon of Mitzpah planted his field [with two different kinds] and came before Rabban Gamaliel. They both went up to the Chamber of Hewn Stone and asked [about the law]. Nahum the scribe said: I have a tradition from Rabbi Meyasha, who received it from Abba, who received it from the pairs [of sages], who received it from the prophets, a halakhah of Moses from Sinai, that one who plants his field with two species of wheat, if he makes up of it one threshing-floor, he gives only one peah, but if two threshing-floors, he gives two peahs.

מַעֲשֶׂה שֶׁזָּרַע רַבִּי שִׁמְעוֹן אִישׁ הַמִּצְפָּה לִפְנֵי רַבָּן גַּמְלִיאֵל, וְעָלוּ לְלִשְׁכַּת הַגָּזִית וְשָׁאָלוּ. אָמַר נַחוּם הַלַּבְלָר, מְקֻבָּל אֲנִי מֵרַבִּי מְיָאשָׁא, שֶׁקִּבֵּל מֵאַבָּא, שֶׁקִּבֵּל מִן הַזּוּגוֹת, שֶׁקִּבְּלוּ מִן הַנְּבִיאִים, הֲלָכָה לְמשֶׁה מִסִּינַי, בְּזוֹרֵעַ אֶת שָׂדֵהוּ שְׁנֵי מִינֵי חִטִּין, אִם עֲשָׂאָן גֹּרֶן אַחַת, נוֹתֵן פֵּאָה אַחַת. שְׁתֵּי גְרָנוֹת, נוֹתֵן שְׁתֵּי פֵאוֹת: