The First Presidency has the following notice hung in all temples: "The following is to be regarded as an established and imperative rule. The garments worn by those who receive endowments must be white and of the approve[d] pattern; they must not be altered or mutilated, and are to be worn as intended, down to the wrist and ankles and around the neck. Admission to the temple will be refused to those who do not comply to these requirements. The Saints should know that the pattern of endowment garments was revealed from Heaven and that the blessings promised in connection with wearing them will not be realized if any unauthorized change is made in their form or in the manner of wearing them." Later, after the garment was changed, this notice was taken down and ordered burned.
[On This Day in Mormon History, http://onthisdayinmormonhistory.blogspot.com]