Herculean vs superhuman

Herculean

adj
  • Of extraordinary might, power, size, etc.; suggesting Hercules in size or strength. 

  • Requiring a huge amount of work; of extraordinary difficulty. 

superhuman

adj
  • Beyond what is possible for a human being. 

noun
  • A human being with remarkable abilities or superpowers. 

How often have the words Herculean and superhuman occurred in a corpus of books? (source: Google Ngram Viewer )