Joseph Smith and Sidney Rigdon Saw Other Things That They Were Commanded Not to Record 

Doctrine and Covenants 76:114–119

114 But great and marvelous are the works of the Lord, and the mysteries of his kingdom which he showed unto us, which surpass all understanding in glory, and in might, and in dominion;
115 Which he commanded us we should not write while we were yet in the Spirit, and are not lawful for man to utter;
116 Neither is man capable to make them known, for they are only to be seen and understood by the power of the Holy Spirit, which God bestows on those who love him, and purify themselves before him;
117 To whom he grants this privilege of seeing and knowing for themselves;
118 That through the power and manifestation of the Spirit, while in the flesh, they may be able to bear his presence in the world of glory.
119 And to God and the Lamb be glory, and honor, and dominion forever and ever. Amen.

Elder Bruce R. McConkie wrote:

“We have that knowledge about the three degrees of glory which is written in section 76, but we do not have a full understanding of those kingdoms of eternal glory, ‘which surpass all understanding in glory, and in might, and in dominion.’ Such added knowledge was received by the Prophet and Sidney Rigdon, but they were forbidden to write it, and it is ‘not lawful for man to utter’ (D&C 76:114–119).”

(The Promised Messiah: The First Coming of Christ [1978], 91.)