Upon request of the First Presidency Elder [Delbert L.] Stapley called and presented samples of the new ceremonial garment which is to take the place of the string garment now being used in the Temples. This new garment will have buttons instead of strings, and [a] closed crotch. It will also have a collar on it. Elder Stapley showed samples of the new ceremonial garments for men and women, and they were approved by me. Letters will be sent to the Presidents of Temples notifying them of this change. This new garment pattern had been presented to the Brethren in the meeting of the council of the First Presidency and the Twelve on January 21, 1965, at which time it was unanimously approved by the Council.
[David O. McKay diary, May 14, 1965, quoted in Anderson, Devery; The Development of LDS Temple Worship, 1846-2000: A Documentary History, http://amzn.to/TempleWorship]