How could Joseph Smith guess that ancient Mesoamerican warriors wore heavy clothing as armor?

In Alma 43:19 we read

And when the armies of the Lamanites saw that the people of Nephi, or that Moroni, had prepared his people with breastplates and with arm-shields, yea, and also shields to defend their heads, and also they were dressed with thick clothing—

Why would Joseph say the armies of the Lamanites wore thick clothing to go to battle? Why would they need that in addition to breast plates and arm shields?

Bruce E. Dale and Brian Dale explain how this corresponds to the Maya:

In both The Maya and the Book of Mormon, thick clothing was used as armor. It is also unusual. We know of no contemporary model or example that Joseph Smith could have relied upon to correctly “guess” this correspondence. Even today we doubt that one person in a hundred would know that ancient Mesoamerican warriors wore heavy cotton clothing as armor.
– Bruce E. Dale and Brian Dale – Joseph Smith: The World’s Greatest Guesser (A Bayesian Statistical Analysis of Positive and Negative Correspondences between the Book of Mormon and The Maya)

Where was Joseph Smith getting all this information from?

See:

Bruce E. Dale and Brian Dale – Joseph Smith: The World’s Greatest Guesser (A Bayesian Statistical Analysis of Positive and Negative Correspondences between the Book of Mormon and The Maya)

Add