Maimonides was suspected of heresy by the rabbis of Spain. The rabbis of Germany decided to send an emissary to meet him personally and see if the charges were founded (I know!). They sent a Rabbi Meir. Upon arriving, Rabbi Meir was, uh, perplexed at the things he witnessed in the Maimonides household. First, a servant placed food which looked like human hands on the table. Secondly, the Rambam summoned another servant, named Peter, to fetch wine for the guest. Finally, Maimonides ordered that a calf be slaughtered for him in a quite unlawful fashion. Completely shocked at the obviously unkosher food (human hands, wine served by a non-Jew, and unschechted meat) Rabbi Meir managed to mumble excuses and didn't eat. Later Maimonides approached him and asked him his impressions. Not being able to answer for fear of offending his host, but obviously assuming that Maimonides was guilty of preparing the treifest of treif dishes, the Rambam explained. First of all, the human hand was a special kind of vegetable which only looks like it is a human hand. Secondly, his faithful servant Peter is Jewish. Hasn't Rabbi Meir ever heard of the Talmudic sage Rabbi Yose ben Patrus? Thirdly, the calf was removed from the womb of a pregnant cow that was slaughtered according to halacha. As you know, the law is that such a calf does not need to be slaughtered according to the method of shechita. Rabbi Meir understood the lesson: do not jump to conclusions about other people without understanding the complete picture. Having learned this great lesson, he returned to Germany and reported that the Rambam is no heretic.
This is only the quickie version. A more fleshed-out version of the story can be read here. If you are like me, you probably read this story in the Tales of the Geonim section of the Jewish Press. Perhaps you read it in Nathan Ausubel's Treasury of Jewish Folklore, or even in Moses Gaster's Ma'aseh Book. I somehow remember someone trying to explain that the food which looked like a hand must have been asparagus. Apparently taking this story as historical, someone suggests that it was a Chinese citron which is, admittedly, a pretty crazy etrog (also known as Buddha's hand):
The aforementioned Ma'aseh Book is in fact the written source of this story.
The Ma'aseh Buch was first printed in Basel in 1602. It is a compendium of nearly 300 stories from the Talmud, Midrashim and later sources. For example, there are many stories about Rabbi Yehuda Ha-chassid, and some about Rashi. Some of them are from known written works, others seem to have been passed down orally (or invented). Here is the title page:
As you can see, the full title was Ein Schein Maaseh Buch ("A Beautiful Story Book"). The title page begins by asking the "dear Men and Women to come here" and peruse the book. The stories, it says, are all from the Gemara, with some from the Midrash Rabbos, Bachya, and that the stories about Rabbi Yehuda Ha-chassid are not to be missed. In addition, there are stories from the Sefer Chassidim, Sefer Mussar and the Yalkut. Then comes a great line: איר ליבן ארויאן איר האט פון דיא טייטשי ביכר אל ואר איצונדר האט איר אך דיא טייטשי גמרא / Dear ladies, you already had German books; now you will have the German Gemara! And who published it? A Litvak. Okay - he was from Mezerich.
Interestingly, on the inside page are some other words explaining that the hope is that the reader will read this pious book, but not read from the Book of Cows. The reference it to the קויא בוך, which was printed in Verona a few years earlier, in 1595. Evidently the Cow Book was popular enough that the compiler of the Story Book hoped that it would supplant the other in popularity. In addition and in particular, it was hoped that such books would not be read on Shabbos. The publisher advises women to buy it quickly before it sells out. Here is the Koy Buch's title page:
I don't know how many copies of the 1602 Maaseh Buch there are, but the first edition of this book would seem to be incredibly rare. In a late 19th century catalog of the Bodleian Library I saw it claimed that only one copy was known (its copy). A few decades later Israel Zinberg writes in History of Jewish Literature that there are three known copies. For all I know a few more have turned up. In addition, there are extant a couple of manuscripts of the book. Gaster's English translation (1934) was preceded by Bertha Pappenheim's translation of the 1723 Amsterdam edition into German (which you can read here).
In any case, here is the story about the Rambam as it appeared in the 1703(?) ורנקבורט edition (click to enlarge):
Some random tidbits. Throughout this version (and three other Maseeh Buchs I looked at) the Rambam is called רבי משה מיימנו. No, that is not a typo. מיימנו. Evidently for the not-so-learned audience, just who he is is explained very carefully. He is a "Gevaltiger Herr in der Torah." As in the Jewish Press version, the story takes place in Spain (which the Rambam fled as a young man). The משרת, or servant, is called פיטר (so all those fancy versions which call him Patros aren't actually being faithful to the source). Not surprisingly he is not called a גוי but איין כותי, a "Samaritan." The Rambam informs Rabbi Meir that Peter is not only Jewish, but he is איין פרומר יוד, he is a pious Jew! The identity of the Talmudic rabbi named Peter (the father, really) is not given. Rather, we are told that a talmid chochom in the Gemara was called Rabbi Peter. After asserting that this Rabbi Meir is the one who coined the famous aporophism that "From Moshe to Moshe there was none like Moshe," at the end the reader is exhorted that חושד בכשרים לוקה בגופו, for suspecting the innocent, the penalty is flogging.
Here is the title page:
Incidentally, the Maaseh Buch was so interesting and so popular, that only a few years after it was printed Christoph Helwig translated dozens of its stories, in two volumes (1611 and 1617) called the Juedischer Historien der Thalmudischer Rabbinischer wunderbarlicher Legenden. Interestingly, while the Maaseh Buch does not carefully list its sources, Helwig apparently researched them, because he gives the rabbinic source of each legend. Before each story he gives the number that it appears in the Maaseh Buch and its source in the Talmud or Midrash, if there is one. In case anyone was wondering, the Rambam story is supposed to be #200. Unfortunately Helwig left it out (but see the note ). By the time of the Frankfurt 1703 edition, which I used, it is #214! The Maaseh Buch grew some maasehs. Here is Helwig's title page:
In case anyone thought that the idea that the content and doings of a Chassidisher newspaper in New York can quickly become general knowledge is something new (for example), one should consider that many oral tales of the Jews were already available in translation only 9 years after their first printing. The pace may have quickened, but the concept is really the same.
 Or the supplement Ma'asei Adonoi, which was subsequently incorporated in later editions. Since I could not see the original 1602 edition of the Ma'aseh Buch, or a copy of Ma'asei Adonoi, I'm not sure where it first appears. Steinschneider in his article on the Maaseh Buch in Serapaeum seems to say that it's in the original, but I'm not 100% sure.