Yoma, Chapter Three, Mishnah Eleven
Alas, along with those who were remembered for praise, there were those who were remembered for shame as well. Interestingly, all of those who were remembered for shame were denounced for the same transgressionthey refused to teach their secrets to outsiders, thereby preserving for themselves monopolies over how certain things in the Temple were run. It is clear that the rabbis were incensed by the preservation of such secrets; both for practical and I believe ideological reasons as well. Practically, their trade was in constant danger of being lost. Ideologically, it seems to me that the rabbis stood for a certain democratization of knowledge. With the exception of certain esoteric subjects, the rabbis believed that people should know the oral tradition. Those who kept its various aspects to themselves were condemning the tradition to be unjustly monopolized and even worse, forgotten.
And these they mentioned to their shame:
1) Those of the House of Garmu did not want to teach anything about the preparation of the showbread.
2) Those of the House of Avtinas did not teach to anything about the preparation of the incense.
3) Hugros, a Levite knew a chapter [concerning] the song but did not want to teach it.
4) Ben Kamtzar did not want teach anyone his art of writing.
5) Concerning the former it is said: The memory of the righteous shall be for a blessing (Proverbs 10:7); concerning the others it is said: But the name of the wicked shall rot.
Section one: The trick with the showbread, according to the Talmud, was to take it off the sides of the oven, where bread was cooked (as is pita today) without it breaking apart due to its size. The House of Garmu (probably not related to gourmet but who knows!) knew how to do this but did not want to teach others.
Section two: The incense was a complicated mixture of spices and some other materials which caused it to turn into thick smoke. The House of Avtinas did not want to teach others how they made the incense.
Section three: Hugros knew certain tricks on how to improve ones voice, but to his discredit, did not wish to teach others.
Section four: According to legend, Ben Kamtzar could take four styluses in one hand and write four letters at the same time.
Section five: Concerning those listed in mishnah ten for praise we say The memory of the righteous shall be for a blessing but concerning those in our mishnah we say, But the name of the wicked shall rot, meaning let their memory be forgotten.