This makes up around half the surviving literature of ancient Greece

Galen began writing as a teenager, and this explains, in part, at least, his extraordinary output - 'fatiguingly diffuse', as one historian put it - some three million words that are collectively known as the Galenic corpus. Astonishingly, this makes up around half the surviving literature of ancient Greece, but is only a fraction of the ten million words he is estimated to have written.

V. Moller, The map of knowledge (2019), 49-50