Reed Smoot Case, vol. 3, p. 185; “…the endowments have never changed and can never change; as I understand it; it has been so testified, and that Joseph Smith Jr., himself was the founder of the endowments.” – Senator Reed Smoot
Revelation 22:8; “But the fearful, and unbelieving, and the abominable, and murderers, and whoremongers, and sorcerers, and idolaters, and all liars, shall have their part in the lake which burneth with fire and brimstone: which is the second death.”
The endowments changed within a year of its inception in 1842 and less than a decade before the Reed Smoot hearings they changed again to ensure all temples were performing the same endowments.
Of course this doesn’t account for the numerous changes that have taken place since the hearings – the latest being in 2008.