Mormon History, Jun 26, 1847. Saturday.

[William Clayton Journal] ...Elder Pratt has gone ahead with the barometer to try to find the culminating point or highest dividing ridge of the South Pass as we are evidently at the east foot of the pass. Fremont represents that he did not discover the highest point on account of the ascent being so gradual that they were beyond it before they were aware of it, although in company with a man who has traveled it back and forth for seventeen years...At 20 minutes past 2 we moved onward, ascending again on pretty high land where we found good traveling. The latitude at our noon halt was 42 [degrees] 22' 42". After traveling seven miles this afternoon we arrived on a level spot of lower land and some grass, and inasmuch as we have found no stream as laid down on Freemont's map since leaving the Sweet Water, neither is there much appearance of any for some miles farther, the wagons halted while President Young and some others went over the ridge to the north to look for a camp ground as some of the brethren said the Sweet Water was close by...Elders Kimball, Pratt and some others are some miles ahead and not having returned at dark, a number of the brethren were sent to meet them. They soon returned in company with Elder Kimball who reported that he had been on as much as six miles to where the head waters of the Atlantic divide from those of the Pacific, that Elder Pratt was camped there with a small party of men direct from Oregon and bound for the U.S. It is now a certainty that we are yet two miles short of the dividing ridge of the South Pass by the road. This ridge divides the headwaters of the Atlantic from those of the Pacific and although not the highest land we have traveled over, it may with propriety be said to be the summit of the South Pass. The Wind River mountains appear very high from this place but on the south there is very little appearance of mountains, Table Rock itself appearing but a little elevated.

[source: George D. Smith, An Intimate Chronicle; The Journals of William Clayton, Signature Books in association with Smith Research Associates, Salt Lake City, 1995, http://amzn.to/william-clayton]