In the most famous of patriarchal blessings, Jacob called his 12 sons together and gave them each a blessing. To his beloved Joseph, he said, Joseph is a fruitful bough, even a fruitful bough by a well; whose branches run over the wall (Gen 49:22). Elder LeGrand Richards interpreted this to mean that there would be a branch of Joseph's posterity which would cross the great oceanic barrier (or wall), "It seems consistent to assume that the ocean was regarded as the wall over which Joseph's branches were to run 'unto the utmost bound of the everlasting hills.'" (A Marvelous Work and a Wonder, p. 64)
Jacob also testified that the part of Joseph's coat of many colors which was preserved was symbolic of a branch of Joseph's posterity which would similarly be preserved. The Bible is silent on this prophecy, but it was contained on the brass plates. Captain Moroni made mention of it as follows, Yea, let us preserve our liberty as a remnant of Joseph; yea, let us remember the words of Jacob, before his death, for behold, he saw that a part of the remnant of the coat of Joseph was preserved and had not decayed. And he said--Even as this remnant of garment of my son hath been preserved, so shall a remnant of the seed of my son be preserved by the hand of God, and be taken unto himself, while the remainder of the seed of Joseph shall perish, even as the remnant of his garment (Alma 46:24). Jacob's son Joseph also prophesied on this subject (see 2 Nephi 3:5 and JST Gen 50:25).