In the pre-exilic texts of the Book of Mormon, we read that Nephi, Lehi, and even other earlier prophets testified that the Messiah would be crucified. For instance, in 1 Nephi 19:10 we read:
And the God of our fathers, who were led out of Egypt, out of bondage, and also were preserved in the wilderness by him, yea, the God of Abraham, and of Isaac, and the God of Jacob, yieldeth himself, according to the words of the angel, as a man, into the hands of wicked men, to be lifted up, according to the words of Zenock, and to be crucified, according to the words of Neum, and to be buried in a sepulchre, according to the words of Zenos, which he spake concerning the three days of darkness, which should be a sign given of his death unto those who should inhabit the isles of the sea, more especially given unto those who are of the house of Israel.
Nephi, in a vision, was shown the then-future crucifixion of Jesus (1 Nephi 11:33):
And I, Nephi, saw that he was lifted up upon the cross and slain for the sins of the world.
Some critics (e.g. James R. White, Letters to a Mormon Elder) have cited this as evidence of an anachronism in the Book of Mormon. However, there are a number of problems with this.
In Lam 5:12, authored by Jeremiah, a contemporary of Lehi et al., we read the following:
Princes are hanged up by their hand: the faces of elders were not honoured.
In this verse, we read of princes being “hanged up by their hand” which is part-and-parcel of what crucifixion entails. Furthermore, this is strengthened by an examination of the LXX which uses the verb κρεμαννυμι. This is the same verb Luke uses of the malefactor in Luke 23:39:
And one of the malefactors which were hanged (κρεμαννυμι) railed on him, saying, If thou be Christ, save thyself and us.
Richard Carrier in his book, On the Historicity of Jesus (Sheffield, 2014), p. 61, provides further evidence that the concept of crucifixion was known by pre-exilic Israelites:
[T]he Bible described one method of execution as to ‘hang in the sun’ (in the Septuagint, literally, exeliazo = ex heliou, ‘out in the sun,’ or apenanti tou heliou, ‘against the sun’), which implies the intent was for the hanged to die from exposure (Numbers 25:4 and 2 Samuel 21:6, 9, 13). That is essentially a form of crucifixion, however it was effected. Likewise, when Joshua hung on trees the king of Ai and the kings of Amorites (Joshua 8:29 and 10:26-27), and when the Law of Moses calls for the executed to be hanged on trees or planks (xulon in the Greek) even when already dead (Deuteronomy 21:22-23), or when Haman and his sons are hung on a giant pole (xulon again in Greek translations of Esther 5:14; 7:9-10; and 8:7), these are all forms of crucifixion.