Reference for Zavim 4:7
הָיָה יוֹשֵׁב עַל גַּבֵּי הַמִּטָּה וְאַרְבַּע טַלִּיּוֹת תַּחַת אַרְבַּע רַגְלֵי הַמִּטָּה, טְמֵאוֹת, מִפְּנֵי שֶׁאֵינָהּ יְכוֹלָה לַעֲמֹד עַל שָׁלשׁ. רַבִּי שִׁמְעוֹן מְטַהֵר. הָיָה רוֹכֵב עַל גַּבֵּי בְהֵמָה וְאַרְבַּע טַלִּיּוֹת תַּחַת אַרְבַּע רַגְלֵי בְהֵמָה, טְהוֹרוֹת, מִפְּנֵי שֶׁהִיא יְכוֹלָה לַעֲמֹד עַל שְׁלשָׁה. הָיְתָה טַלִּית אַחַת תַּחַת שְׁנֵי יָדַיִם, תַּחַת שְׁנֵי רַגְלַיִם, תַּחַת יָד וָרֶגֶל, טְמֵאָה. רַבִּי יוֹסֵי אוֹמֵר, הַסּוּס מְטַמֵּא בְרַגְלָיו וְהַחֲמוֹר בְּיָדָיו, שֶׁמִּשְׁעֶנֶת הַסּוּס עַל רַגְלָיו וּמִשְׁעֶנֶת הַחֲמוֹר עַל יָדָיו. יָשַׁב עַל קוֹרַת בֵּית הַבַּד, כֵּלִים שֶׁבָּעֵקֶל טְמֵאִין. עַל הַמַּכְבֵּשׁ שֶׁל כּוֹבֵס, כֵּלִים שֶׁתַּחְתָּיו, טְהוֹרִין. רַבִּי נְחֶמְיָה מְטַמֵּא:
If he [a <i>zav </i>] sat on a bed and there were four cloaks under the four legs of the bed, they are unclean, because [the bed] cannot stand on three [legs]. Rabbi Shimon renders them clean. If he [a <i>zav </i>] was riding on an animal and there were four cloaks under the four legs of the animal, they are clean, because [the animal] can stand on three [legs]. [If] there was one garment under its two forelegs [or] under its two hindlegs, [or] under a foreleg and a hind leg it is unclean. Rabbi Yose says, A horse imparts uncleanliness through its hind legs and the donkey through its forelegs, for a horse leans on it hind legs and a donkey leans on its forelegs. If he [a <i>zav </i>] sat on the beam of an olive press, the utensils in the rope-basket [where the olives are kept during the pressing process] are unclean. If he [a <i>zav </i> sat] on the laundryman's clothing- press, the utensils beneath them are clean. Rabbi Nechemia renders them unclean.