Where are the magic cucumbers discussed in the Gemara by a Rabbi proud of his knowledge? Are magic cucumbers discussed elsewhere? Thanks.
These were some of the final words of R' Eliezer, as he lay on his deathbed.
'Moreover, I have studied three hundred, (or, as others state, three thousand laws) about the planting of cucumbers [by magic] and no man, excepting Akiba b. Joseph, ever questioned me thereon. For it once happened that he and I were walking together on a road, when he said to me, "My master, teach me about the planting of cucumbers". I made one statement, and the whole field [about us] was filled with cucumbers. Then he said, "Master, you have taught me how to plant them, now teach me how to pluck them up". I said something and all the cucumbers gathered in one place'
R' Eliezer had been placed under a ban, which lasted until he died, so he was bemoaning the fact that all his specialized knowledge was going to waste.
This story is brought by the Gemara in response to the mishna that Ariel quoted.
The Mishnah about Magic cucumbers appears in Sanhedrin. It discusses the case of whether a person used an actual maseh or just "achizas enayim" to raise cucumbers:
ז,יא המכשף--העושה מעשה, ולא האוחז את העיניים. רבי עקיבה אומר משום רבי יהושוע, שניים לוקטין קישואים--אחד לוקט ופטור, ואחד לוקט וחייב; העושה מעשה חייב, והאוחז את העיניים פטור.