Mormon History, Dec 12, 1845

[Anointed Quorum] At 10:15 a.m., the general membership of the LDS church began receiving the anointing and endowment ordinances in the Nauvoo temple, and the apostles continued the initiations until midnight. Every, Sunday morning until he closed the Nauvoo temple in February 1846, Brigham Young conducted a prayer circle meeting to which all endowed persons were imvited. Continuing the previous terminology, he told these newly endowed people that they were also members of the "First Quorum" established by the martyred prophet. However, when the newly endowed numbered in the hundreds, it was no longer possible for every interested person to participate in the prayer circle. Within weeks thousands had been endowed, and the temple was too small to accommodate a meeting of everyone who had joined the "First Quorum." After the Mormons left Nauvoo, the term became a nostalgic memory, especially for those initiated during Joseph Smith's administration.

[source: Quinn, D. Michael, The Mormon Hierarchy: Origins of Power, Signature Books, 1994, Appendex: Meetings and Initiations of the Anointed Quorum, 1842-45, http://amzn.to/origins-power]