Related על בבא מציעא 111:2

They did not permit selling Demai except to a wholesale dealer (=סיטון, per Jastrow). A homeowner who sells both this and that (i.e., both large and small quantities, per Lieberman) needs to tithe, the words of Rabbi Meir. But the Sages say, one wholesale dealer and one homeowner are permitted to sell [Demai] and to send it to their friend, and give it to him as a present.