Tosefta sobre Kelim 5:13

Four things Rabbi Eliezer declares pure while the Sages declare impure. The rim of a stone strainer—Rabbi Eliezer says: It is not impure in the air; but the Sages say: It is impure in the air. A baker's sheet which is fixed to a nail, or attached to a beam—Rabbi Eliezer makes it pure; but the Sages make it impure. A shoe that is on the shoe mold—Rabbi Eliezer makes it pure; but the Sages make it impure. He cut it [an oven, see Mishnah Kelim 5:10] into rings, and sand is placed between each ring, Rabbi Eliezer makes it pure; but the Sages make it impure. This was called the oven of Akhnai, for on its account, disagreement (mahloket) increased in Israel.