Just ran across this Smithsonian.com article: The Top 10 Books Lost to Time. Neat read, rife with possibilities; every link I’ve seen pulls a quote from the #4 selection, Inventio Fortunata, which does have a bit of a Piri Reis-sounding mystery to it; but the “lost” Shakespeare work of Cardenio interests me more:

Cardenio has been called the Holy Grail of Shakespeare enthusiasts. There is evidence that Shakespeare’s company, the King’s Men, performed the play for King James I in May 1613—and that Shakespeare and John Fletcher, his collaborator for Henry VIII and Two Noble Kinsmen, wrote it. But the play itself is nowhere to be found.

And what a shame! From the title, scholars infer that the plot had something to do with a scene in Miguel de Cervantes’ Don Quixote involving a character named Cardenio. (A translation of Don Quixote was published in 1612 and would have been available to Shakespeare.)

Kind of sounds like the ultimate Elizabethan-era crossover.