Trecena 17 opens on 1 Atl, water, under the patronage of Chalchiuhtotolin, the jade turkey, a penitential aspect of Tezcatlipoca associated in the sources with disease and its cure, invoked when a petitioner sought forgiveness for a ritual fault or a broken observance. The water week runs unquiet: fortune under it read as a current, carrying away the careless, and its remedy, per the readers' formula, was penance directed to the sign's stern patron, an unfavourable trecena that answered correction rather than one that could simply be endured until it passed.
Chalchiuhtotolin's patronage of purification through penance, distinct from Tlazolteotl's confession rite though related in its concern with clearing ritual fault, gave this trecena a specific remedial path the tonalpouhque could recommend to a family troubled by its reading, a concrete offering or observance rather than only a general caution to be careful. Water's own instability as a symbol, capable of nourishing or of sweeping away depending on how it moves, matches the trecena's reading precisely, and Tezcatlipoca's several aspects across the tonalpohualli, appearing here as the jade turkey and elsewhere as the frost lord Itztlacoliuhqui and the mountain jaguar Tepeyollotl, together make him the single deity whose different faces patronise the largest share of the count's more demanding trecenas.