In Company with President Kimball I visited President B Young. We found him feeble but much recoverd. The sickness had mostly left President Young as soon as he came over the big mountain [on present-day highway 65 between Mountain Dell and East Canyon Resivour] this way. There seemed to be sumthing mysterious about his sickness. ... Presidents Kimball & Grant administered unto him & prayed for him & he began to recover.
The brethren felt that the valley was full of Devils. They had to go onto the mountain before they could get the spirit of prayer. They felt that there was a Legion of Devils in the valley congregated against them & trying to destroy them. They felt also that there was evil intended against them on the road & that they should leave the valley & return home. They hitched up their Horses in the morning & started for home & the nearer they drew to the City the better they felt. [They had travelled to Fort Supply & Fort Bridger.]
[Source: Wilford Woodruff's Journal: 1833-1898 Typescript, Volumes 1-9, Edited by Scott G. Kenney, Signature Books 1993, http://amzn.to/newmormonstudies]