A lot of people haven't read it, so I'll post it below.
It was Oliver Cowdery who ordained and blessed the original Twelve. In some cases, the minutes note that Martin Harris and David Whitmer assisted. For other cases, we can infer that all three witnesses participated in the ordination, but the record is not clear.
Traditionally, we've all been taught that the Three Witnesses ordained the original Twelve. That's why everyone's Priesthood line of authority shows the Three Witnesses. It's possible that happened, but the record for February 14, 1835, shows that the Three Witnesses ordained (blessed) Lyman Johnson, Brigham Young, and Heber C. Kimball.
The minutes say that on Feb. 15, 1835, "President Cowdery called forwarward [sic] Orson Hyde, David W. Patten and Luke Johnson and proceeded to their ordination & blessing."
After recording the blessings of these three men, the minutes record the "blessing" of William E. McLellin, John F. Boynton, and William Smith, without explaining who ordained them.
Later, on Feb. 21, Parley P. Pratt was ordained as one of the Twelve by Joseph Smith, David Whitmer, and Oliver Cowdery. Oliver acted as voice and after the ordination, gave Elder Pratt a charge.
The same day Oliver Cowdery "blessed" Thomas B. Marsh. David Whitmer sealed that blessing. Then Orson Pratt was ordained and David Whitmer confirmed the ordination. Following that blessing, Prsident Cowdery gave the charge to the Twelve (below).
The Three Witnesses received their priesthood authority this way:
Oliver Cowdery - Peter, James and John
David Whitmer - ordained a High Priest by Oliver Cowdery on October 25, 1831
Martin Harris - ordained a High Priest by Lyman Wight on June 3, 1831. Wight had been ordained an Elder by Oliver Cowdery on Nov. 20, 1830. [Note: Wight was ordained to the "high Priesthood" by Joseph Smith in June 1831, and then Wight ordained Joseph Smith to the "high Priesthood" at the same meeting.]