[David O. McKay and counselors]
It has come to our attention that in some of the temples[,] instruction has been given to those going through to receive their endowments prior to entering into the marriage covenant that they must not remove the temple garment during the time of sexual relations. We have authorized no such instruction or advice. We feel that this is a matter of such intimate nature that it must be left with the persons concerned. We therefore ask that you govern yourselves accordingly.
[Source: David O. McKay, Hugh B. Brown, and N. Eldon Tanner to temple presidents, May 22, 1968, in Anderson, Devery; The Development of LDS Temple Worship, 1846-2000: A Documentary History, http://amzn.to/TempleWorship]