[Apostle Wilford Woodruff Journal]
Among the vast number of the Keys of the Kingdom of God Joseph presented the following one to the Twelve for there benefit in there experience & travels in the flesh which is as follows:
In order to detect the devel [devil] when he transforms himself nigh unto an angel of light. When an angel of God appears unto man face to face in personage & reaches out his hand unto the man & he takes hold of the angels hand & feels a substance the same as one man would in Shaking hands with another he may then know that it is an angel of God, & he should place all Confidence in him. Such personages or angels are Saints with there resurrected Bodies.
But if a personage appears unto man & offers him his hand & the man takes hold of it & he feels nothing or does not sens any substance he may know it is the devel [devil], for when a Saint whose body is not resurrected appears unto man in the flesh he will not offer him his hand for this is against the law given him & in keeping in mind these things we may detec the devil that he decieved us not.
[Wilford Woodruff's Journal: 1833-1898 Typescript, Volumes 1-9, Edited by Scott G. Kenney, Signature Books 1993, http://amzn.to/newmormonstudies]