Atl, water, is read as purification and as release, and Nahua thought paired water directly with fire in the compound figure atl tlachinolli, burnt water, the emblem of war carried in codices as a stream of water and a stream of flame crossed together, a striking image that ties this gentle sounding sign to one of Mexica religion's most consequential concerns. The augural readings themselves are unquiet: water takes its own course rather than a fixed one, and Sahagun's informants read the water day's children with that same unpredictability, a fortune that could nourish or could as easily overflow its banks depending on circumstances the reading alone could not fully specify.
The atl tlachinolli emblem's pairing of this sign with fire specifically, rather than with any of the count's other nineteen signs, reflects the day's own patron, a fire deity, a coincidence of patron and symbol that gave Atl a doubled elemental character few other signs carry as explicitly. Water's association with the newborn's ritual bathing elsewhere in Mexica practice, though governed by a different deity than this day sign's own patron, meant Atl's reading touched both the beginning of a life, through purification, and the ending of many lives, through the war emblem its name helped form.