D&C 8:6-9 “Now this is not all thy gift” to Oliver Cowdry, referring to the rod he used to get revelation.

Joseph Smith Papers: original D&C 8 (then known as the Book of Commandments, 1833 edition): speaks of the “gift of Aaron” which Oliver Cowdry has as being a “rod of nature” and “sprout”. See http://josephsmithpapers.org/paperSummary/revelation-april-1829-b-dc-8?p=2

Heber C Kimball had a rod for revelation: Bro Kimball showed me a rod that the Lord through the prophet Joseph had given to him. He said that when he wanted to find out anything that was his right to know, all he had to do was to kneel down with the rod in his hand, and that sometimes the Lord would answer his questions before he had to time to ask him.

5 Friday 1844 inquired by the rod of the Lord if my family was well (Heber C. Kimball Journal [1844-1845]
Thursday prayer meeting in the afternoon with the Twelve, went home and used the Rod; I got a witness Elder W Richards would live, that we would overcome our enemies (H.C. Kimball Journal 5 September 1844)
I went up to the capital in DC. I see men and their wives walking out two by two. O that I had my dear Vilate with me. Bless her heart and soul and body… I called on the name of the Lord he heard me for my heart was made comfortable. I inquired by the rod it was said my wife would come to me in the East, and that Congress would not do anything for us. I do not care whether they do or not. It is none of theirs to give. My Father in heaven owns it all and he will give it to so let them go their own place, good night. I must go to bed. (Heber C Kimball “Journal“ Church Historical Department; Ms/f/50,51; spelling updated)

God has used physical objects as instruments of revelation to testify of Christ. Modern and ancient examples, including Aaron’s ancient rod which Oliver Cowdry used. Truman G Madsen suggested that the reason the Book of Mormon characters had to carry the gold plates around in the desert with them in their travels is because without it we forget. He referenced President George Albert Smith in saying that without memorials, we forget things. This could also by why Joseph Smith recovered the gold plates to translate rather than merely getting it by revelation from God the whole time.

“It should be recognized that such tools as the Urim and Thummim, the Liahona, seer stones, and other articles have been used appropriately in biblical, Book of Mormon, and modern times by those who have the gift and authority to obtain revelation from God in connection with their use. At the same time, scriptural accounts and personal experience show that unauthorized though perhaps well-meaning persons have made inappropriate use of tangible objects while seeking or claiming to receive spiritual guidance. Those who define folk magic to include any use of tangible objects to aid in obtaining spiritual guidance confound the real with the counterfeit. They mislead themselves and their readers.” (Dallin H. Oaks, “Recent Events Involving Church History and Forged Documents,” Ensign (October 1987), 63.)

“Some people have balked at this claim of physical instruments used in the divine translation process, but such aids to facilitate the communication of God’s power and inspiration are consistent with accounts in scripture. In addition to the Urim and Thummim, the Bible mentions other physical instruments used to access God’s power: the rod of Aaron, a brass serpent, holy anointing oils, the Ark of the Covenant, and even dirt from the ground mixed with saliva to heal the eyes of a blind man.” (“Book of Mormon Translation,” Gospel Topics on LDS.org (2013).)

Consulted: http://en.fairmormon.org/Doctrine_and_Covenants/Oliver_Cowdery_and_the_%22rod_of_nature%22

More rod studies: Num. 17:8; Ex. 7:9-12