heavy clay Barbara J. Williams, "Pictorial Representation of Soils in the Valley of Mexico: Evidence from the Codex Vergara," Geoscience and Man 21 (1980), 51–62; see p. 54.
you (second person singular subject prefix); we (first person plural subject prefix)
James Lockhart, Nahuatl as Written: Lessons in Older Written Nahuatl, with Copious Examples and Texts (Stanford: Stanford University Press and UCLA Latin American Studies, 2001), 1.