James Hall traces the difficulties the much valorized Raphael poses for biographers:
The Raphael cult was helped by the fact that very little is known about his opinions or “inner life”: he was an unsullied blank canvas. Unlike Leonardo and Michelangelo, he didn’t write many letters or poems or theorize or jot down ideas and shopping lists next to his sketches. What admirers had instead, from the beginning of the eighteenth century, was his skull, exhibited in the Accademia di San Luca in Rome. As part of their initiation, each new student had to place his pencil on it. Goethe, as a kind of climax to his Italian Journey of 1786–8, visited the Academy to marvel at the “brain-pan of beautiful proportions” (he had a cast sent home to Germany, to meditate daily on it). This skull worship only stopped in 1833, when Raphael’s tomb in the Pantheon was opened in the presence of the Pope and other dignitaries, and the skeleton was found to be intact; somewhat disappointingly, the large larynx, still intact and pliable, suggested he had a loud voice.
Read more about the skull of Raphael here.
(Lithograph of the skull of Raphael via the Wellcome Collection)