This slightly complex charm to cross a river or running water safely requires the traveler to apply juice from the plants called yauhtli  and tepepapaloquilitl  to the chest, to have the stones beryl and sardonyx as well as an oyster , and to keep the eyes of a large fish enclosed securely in the mouth.
The beryl is to be held in the hand. It’s unclear to me from the manuscript whether the sardonyx and the oyster are also held in the hand or kept in the mouth with the fish eyes.
Near as I can tell, these herbs are specified because they are sacred to the god Tlaloc, the lord of rain and celestial waters.
I think I’d need a charm to help me be brave enough to try this charm.
 Mexican marigold, Tagetes lucida
 lit. mountain butterfly weed; could be another type of marigold, or Porophyllum punctatum, or one of a number of plants called deer herb depending on who you ask.
 Probably. The translator was not entirely sure. If it’s an oyster, it would be sans shell.
The De La Cruz-Badiano Aztec Herbal of 1552. William Gates, trans. The Maya Society, Baltimore: 1939, p. 103.
“Four Hundred Flowers: The Aztec Herbal Pharmacopoeia, Part 1, Yauhtli and Cempoalxochitl.” Mexicolore. 27 Jan. 2008. Accessed 25 April 2021. Available at http://www.mexicolore.co.uk/aztecs/health/aztec-herbal-pharmacopoeia-part-1.