From Royal Academy's Aztecs exhibit catalogue entry written by J.Ostapkowicz (2004):
PROVENANCE: Gabriel Fejéváry collection (1780-1851), Joseph Mayer collection (1855-67), donated to Liverpool Museum in 1867.
The Codex Fejervary Mayer is a tonalmatl – a ‘book of days and destinies’ which merges time with the course/trajectory of people’s life and fortunes. Its pages depict a series of sophisticated and interconnected calendars – a yearly cycle of 365 days (18 scores of 20 days, + 5 ‘useless’ days) and the ritual calendar – or tonalpohualli – of 260 days (20 named days and 13 numbers). The complex interweave of these calendars with icons such as the 9 Night Lords, 13 deities and 13 quecholli (‘fliers’ or birds) brings together a multivalent ‘reading’ of the text, informing upon a myriad of issues – from human life, labour and behaviour to tribute and economy. The Fejervary Mayer Codex consummately combines the calendars with the tribute system: side 1 deals with commodity items supplied over the year, side 2 deals with people’s labour over the 260-day calendar.
In the hands of the ritual practitioners and other high-status individuals (such as the pochteca, or merchants), the codex became a source of guidance for people’s actions. The screenfold’s internal reading structure was right to left and was determined by the number-and-sign sets of the calendar: how the images and symbols cross-referenced each other was then interpreted by the reader, who was well versed in the significance of the different icons. Although an object of great reverence, the codex was also a tactile, malleable reference tool: a reader could consult both sides simultaneously by folding parts of the codex onto itself. The reading informed on appropriate days to travel, to celebrate a deity’s beneficence with sacrifices, to plant crops or to name a child.
Codices were of pivotal importance in the ordering of the Mesoamerican world. Histories, geneologies and tribute economies were recorded in the pages of xiuhtlapoualli (annals) while the tonalamatl informed on appropriate actions– from everyday events to guidance on major ceremonies and wars. As such, codices served both educational and ritual purposes. At the same time, they were objects of great cultural, literary and artistic value. Tlacuilos, or scribes, were specialists in tlacuilolli (‘that which is written and painted’) and were well respected for their abilities in recording the complexities and nuances of Mesoamerican life.
Although whole libraries were burnt during the time of the Spanish invasion, and only a handful of pre-Cortasian documents survive, the use of the tonalpohualli continues in importance among certain Guatemalan and southern Mexican households.