I asked Sister [Camilla] Kimball about the revelation of June 9 . She said she did not learn of it until a friend of hers called her sometime after the announcement. Said President Kimball had not said a word to her about it in advance. Said she knew he had great anxiety for several days before the announcement, but didn't know what. He had great anxiety because he didn't know for sure how it would be received.
[Source: Confessions of a Mormon historian : the diaries of Leonard J. Arrington, 1971-1997, Gary James Bergera, editor, Signature Books, 2018]