Reference for Kilayim 3:3
הָיָה רֹאשׁ תּוֹר יָרָק נִכְנָס לְתוֹךְ שְׂדֵה יָרָק אַחֵר, מֻתָּר, מִפְּנֵי שֶׁהוּא נִרְאֶה כְּסוֹף שָׂדֵהוּ. הָיְתָה שָׂדֵהוּ זָרוּעַ יָרָק, וְהוּא מְבַקֵּשׁ לִטַּע בְּתוֹכוֹ שׁוּרָה שֶׁל יָרָק אַחֵר, רַבִּי יִשְׁמָעֵאל אוֹמֵר, עַד שֶׁיְּהֵא הַתֶּלֶם מְפֻלָּשׁ מֵרֹאשׁ הַשָּׂדֶה וְעַד רֹאשׁוֹ. רַבִּי עֲקִיבָא אוֹמֵר, אֹרֶךְ שִׁשָּׁה טְפָחִים וְרֹחַב מְלֹאוֹ. רַבִּי יְהוּדָה אוֹמֵר, רֹחַב כִּמְלֹא רֹחַב הַפַּרְסָה:
If a triangular corner point of herbs enters into a field of a different herb it is permitted [it is not considered <i>kilayim</i>], because it is obvious that it is the end of the field. If the field was sown with [one species of] herbs and he wishes to plant in it one row of different herbs, Rabbi Yishmael says, [he may do so] providing that the furrow is open [runs through] from one end of the field to the other. Rabbi Akivah says, the length [of the furrow] must be six handbreadths and the width must be its fullsize [six handbreadths]. Rabbi Yehudah says, [the furrow must be] the width of a full footstep [one handbreadth].