Wilford Woodruff notes in journal for March 1877 that Brigham Young was laboring all winter to produce a perfect form of the Temple Endowment.
Wilford Woodruff, Journal, March 21, 1877, MS 1352, Church History Library
I spent the day in the Temple. We gave Endowments to 183 persons [mostly?] for the dead. W Woodruff sealed 41 persons & E Snow 7, Total 48. Presidet Young has been laboring all winter to get up a perfect form of Endowments as far as possible. They having been perfected I read them to the Company today.