Elder Charles A. Callis of the Council of the Twelve recently received a letter from Patriarch James H. Wallis, relative to a family residing in your mission, who are desirous of receiving their patriarchal blessings, but Brother Wallis says that the woman has colored blood in her veins, although neither she nor her husband is aware of this fact.
In Elder Callis' reply, which we fully endorse, he suggested that Brother Wallis excuse himself from giving these people blessing, but that under no circumstances should he intimate to them or any one else that the woman has colored blood. The consequences of s doing might be very serious, and it is almost an impossibility to prove a thing of this kind.
No doubt Brother Wallis has shown you Elder Callis' letter or informed you of its contents, but in case he has not done so we are desirous that you too should be informed of our attitude regarding such cases.
[First Presidency, Letter to John V. Bluth, as quoted in Minutes of the Apostles of The Church of Jesus Christ of Latter-day Saints, 1910-1951, Privately Published, Salt Lake City, Utah 2010]