cream of the crop vs ne plus ultra

cream of the crop

noun
  • The best or most desirable among some selection. 

ne plus ultra

noun
  • The perfect or most extreme example of its kind; the ultimate. 

  • A prohibition against proceeding further; an insuperable obstacle or limiting condition. 

  • The highest, ultimate point of achievement which can be reached; perfection. 

How often have the words cream of the crop and ne plus ultra occurred in a corpus of books? (source: Google Ngram Viewer )