Ohalos16: 2
כֵּיצַד? כּוּשׁ שֶׁהוּא תָחוּב בַּכֹּתֶל, כַּחֲצִי זַיִת מִתַּחְתָּיו וְכַחֲצִי זַיִת מֵעַל גַּבָּיו, אַף עַל פִּי שֶׁאֵינָן מְכֻוָּנִין — טָמֵא. נִמְצָא מֵבִיא אֶת הַטֻּמְאָה לְעַצְמוֹ בְּכָל שֶׁהוּא. הַקַּדָּר שֶׁהוּא עוֹבֵר וְהַסַּל עַל כְּתֵפוֹ, וְהֶאֱהִיל צִדּוֹ אַחַת עַל הַקֶּבֶר — הַכֵּלִים שֶׁבַּצַּד הַשֵּׁנִי טְהוֹרִין. אִם יֵשׁ בַּסַּל פּוֹתֵחַ טֶפַח — טְמֵאִים. הַתְּלוּלִיּוֹת הַקְּרוֹבוֹת בֵּין לָעִיר בֵּין לַדֶּרֶךְ, אֶחָד חֲדָשׁוֹת וְאֶחָד יְשָׁנוֹת — טְמֵאוֹת. הָרְחוֹקוֹת: חֲדָשׁוֹת — טְהוֹרוֹת, וִישָׁנוֹת — טְמֵאוֹת. אֵיזוֹ הִיא קְרוֹבָה? חֲמִשִּׁים אַמָּה, וִישָׁנָה? שִׁשִּׁים שָׁנָה, דִּבְרֵי רַבִּי מֵאִיר. רַבִּי יְהוּדָה אוֹמֵר: קְרוֹבָה — שֶׁאֵין קְרוֹבָה מִמֶּנָּה, וִישָׁנָה — שֶׁאֵין אָדָם זוֹכְרָהּ.
How so? [If] a spindle was embedded in a wall and there is [a piece of corpse] half the size of an olive beneath it, and another piece half the size of an olive above it — even though they are not one above the other — [the spindle] is tamei. Thus, it spreads tumah onto itself no matter what size it is. [If] a person who sells [earthenware] pots was passing [by a grave] with a car-rying pole on his shoulder, one end of which forms a roof over a grave, the utensils on the other end [of the pole] remain tahor. [However,] if the carrying-pole is a handbreadth wide, [the utensils] become tamei. Mounds that are near either a town or a road are tamei, whether they are new or old. [However, concerning] the distant ones: Those that are new are tahor, whereas the old ones are tamei. What is meant by near? [Within] fifty cubits. And [what is considered] old? [Any that are] sixty years old, these are the words of R’ Meir. R’ Yehudah says, ‘‘near’’ means that no other is closer, and ‘‘old’’ means that no one remembers it.