The first documented description of mountain sickness: the Andean or Pariacaca story.

We describe here for the first time the actual route that Acosta took when he described mountain sickness so vividly in the sixteenth century. We have shown that when Acosta mentioned Pariacaca as the geographical site where he experienced high altitude sickness, this referred not only to the modern peak of Pariachaca, but to the snow covered mountains by this Cerro, and the Central Maritime Andean Range in Peru. In addition, the name Pariacaca also referred to a tambo or inn located on the plateau or Puno of Pariacaca. The location of this route has been obtained by locating primary descriptions on maps from the sixteenth to the eighteenth centuries. Using twentieth century maps, we have been able to identify the described sites along the road and the trail which still exists by them. In addition, using detailed topographical maps, an altitude profile of the trail was obtained. The maximum altitude on this trail or old road reached 4800 m (15750 ft), about the same elevation as the summit of Mt. Blanc, the highest mountain in western Europe.