ballot box vs show of hands

ballot box

noun
  • The process or method of voting. 

  • A sealed box with a slit, into which a voter puts a completed voting slip. 

show of hands

noun
  • A vote in which people raise a hand in order to state their agreement with something. 

How often have the words ballot box and show of hands occurred in a corpus of books? (source: Google Ngram Viewer )