The Vavasor Papers are a collection of the writings of the Vavasor twins on various aspects of mathematics. Since their deaths, a number of people have been permitted to view the contents of the papers but their attempts at interpretation have mostly been defeated by the rambling nature of much of the mathematical arguments and the brothers' appalling handwriting.
There isn't even any real consensus as to which problems the Vavasors were working on at the time of their death, although there is a rumour that they were about to announce a proof of the Riemann hypothesis. This has developed its own mythology in which the proof was so complex it could only be formulated by a pair of identical twins. There is a more extreme corollary to this, which was that this proof could only be understood by pairs of identical twins. This has led to several candidates including the Russian Korsakov twins, the Austrian Dolmetsches and two of the Indian Kumar triplets being given privileged access to the Vavasor papers, although this all came to an end following the notorious Glühwein incident.
The Marginalia (always with a capital M) are also of considerable interest as a clue to the brothers' psychological state at the time of their deaths, although once again these scribbles are open to many interpretations, as George Burgess found to his cost.