In this post I would like to highlight some intriguing research carried out and sent to me by Andrés Eloy Martínez Rojas, president of la Sociedad Astronómica Urania (SAU) in Morelos, Mexico, relating to folio f68r.  This illustration shows what he is suggesting as an interpretation:

 
You can find a report in Spanish here from a Mexican newspaper and also a rather sketchy and dismissive blog report by Klaus Schmeh in English here.
In essence, Andrés offers the suggestion that the folio in question depicts an annular eclipse of the sun that occurred on April 15th 1409 –  in other words an event when the Moon covers the Sun’s centre, causing the Sun’s visible outer edge to create an apparent “ring … Continue reading f68r – an eclipse in 1409?