Related על ביצה 1:8

If he picks legumes on the holiday, R. Yehuda says: The House of Shammai says: If the pebbles outweigh the edible ones, then he picks out the edible ones and leaves the pebbles lying around; but the House of Hillel says he reads what he wants.

Elazar ben R. Zadok said: The members of the house Rabban Gamliel used to fill a bucket with lentils, douse them with water and skim off, the pebbles sink down, but the edible remains above.