Reference for Yoma 75:6
הוגרס בן לוי היה יודע פרק בשיר ולא רצה ללמד בן קמצר לא רצה ללמד על מעשה הכתב על הראשונים נאמר (משלי י, ז) זכר צדיק לברכה ועל אלו נאמר (משלי י, ז) ושם רשעים ירקב
which shone like gold. <big><b>MISHNAH: </b></big>AND THESE WERE MENTIONED TO THEIR SHAME: THEY OF THE HOUSE OF GARMU WOULD NOT TEACH ANYTHING ABOUT THE PREPARATION OF THE SHEWBREAD;<span class="x" onmousemove="('comment',' The twelve shewbread loaves, resting in the Hekal on the golden table from Sabbath to Sabbath (Ex. XXV, 30 and Lev. XXIV, 5-9) were very thin and fragile. Made of some four quarts of flour, they were about one half inch in thickness, some twenty-eight inches in length, some twelve inches in breadth. There were some artistic devices at the corners, which made the preparation a highly difficult art. They would be baked on Friday, often on Wednesday, to be eaten on the Sabbath of the following week, and extraordinary skill was required to keep them fresh and well-tasting. The secret of the baking and removing them, from the oven without breaking them was kept by the house of Garmu, for failure to reveal which they are branded here. The Talmud, however, adduces some mitigating reasons for this apparent niggardliness.');"><sup>7</sup></span> THEY OF THE HOUSE OF ABTINAS WOULD NOT TEACH ANYTHING ABOUT THE PREPARATION OF THE INCENSE; HYGROS, SON [OF THE TRIBE] OF LEVI KNEW A CADENCE<span class="x" onmousemove="('comment',' A somewhat difficult phrase. Evidently in connection with the Temple songs. It may have been a specially composed finale, allowing for individual margins of musical ingenuity (Baneth) .');"><sup>8</sup></span>