exemplar vs touchstone

exemplar

noun
  • A well known usage of a scientific theory. 

  • A handwritten manuscript used by a scribe to make a handwritten copy; the original copy of what gets multiply reproduced in a copy machine. 

  • A role model. 

  • Something fit to be imitated; an ideal, a model. 

  • A pattern after which others should be made; an archetype. 

  • A copy of a book or piece of writing. 

  • Something typical or representative of a class; an example that typifies. 

touchstone

noun
  • A standard of comparison or evaluation. 

  • A stone used to check the quality of gold alloys by rubbing them to leave a visible trace. 

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