Statistics for occurrence #1 of “Mexico” in chapter 4 of Thomas Wentworth Higginson, A book of American explorers:
...up that river over fifty leagues they kill great numbers.
[Cabeza de Vaca crossed the Mississippi, or passed its mouth, many years before De Soto reached it. Having finally arrived at the city of Mexico , he was sent home to Europe, and reached Lisbon Aug. 15, 1537.
His later adventures will be found in Southey's Hist.
of Brazil, chap.
v.]
...