envision vs think of

envision

verb
  • To conceive or see something within one's mind. To imagine. 

think of

verb
  • To create in one's mind; to originate an idea through thought. 

  • Used other than figuratively or idiomatically: see think, of. (to think on the subject of) 

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