One of the rarest manuscripts in the world has been revealed hidden beneath the pages of an equally rare but later Mexican codex, thanks to hi-tech imaging techniques.



The Codex Selden, a book of concertina-folded pages made out of a five-metre strip of deerhide, is one of a handful of illustrated books of history and mythology that survived wholesale destruction by Spanish conquerors and missionaries in the 16th century.

A covered-up page with a page from the Codex Selden. Photograph: Bodleian

Researchers using hyperspectral imaging, a technique originally used for geological research and astrophysics, discovered the underlying images hidden beneath a layer of gesso, a plaster made from ground gypsum and chalk, without damaging the priceless later manuscript.

The underlying images must be older than the codex on top, which is believed to have been made about 1560 and was donated to Oxford’s Bodleian library in the 17th century by the scholar and collector John Selden.

The codex is one of fewer than 20 dating from before or just after the colonisation, which were saved by scholars who realised the importance of the strip cartoon-like images, a complex system that used symbols, stylised human figures and colours to recount centuries of history and beliefs, including religious practice, wars, the founding of cities and the genealogy of noble families.

One Spanish witness of the destruction wrote that people were distraught to see their books – and their history – burn, anguished “to an amazing degree, and which caused them much affliction”. Of those known to have escaped the bonfires, the Bodleian had five, the largest group in the world – and now it has six.

Scholars at the Bodleian and the universities of Leiden and Delft, in the Netherlands, are still analysing the newly revealed images, but believe they are unique, a previously unknown genealogy that may help unlock the history of archaeology sites in southern Mexico.

Some of the pages have more than 20 characters sitting or standing, similar to other Mixtec manuscripts – from the Oaxaca region of modern Mexico – which are believed to depict kings and their councils, but uniquely in this case depicting men and women. One so far unidentified figure appears repeatedly, and is symbolised by a twisted cord and a flint knife.

Other pages include people walking with sticks and spears, women with red hair or elaborate headdresses, and what appear to be place names with symbols for rivers.

The researchers, who publish their work this month in the Journal of Archaeological Science: Reports, had been trying a variety of non-invasive techniques to unlock the secrets of the codex, but x-ray examination had revealed nothing.