Spanish donkey vs vaulting horse

Spanish donkey

noun
  • A torture device consisting of a very narrow vertical surface where the victim is supposed to sit with heavy objects attached to their feet. 

vaulting horse

noun
  • An apparatus with an upholstered body but no pommels; since about 2000 replaced with vault, also called vaulting table. 

How often have the words Spanish donkey and vaulting horse occurred in a corpus of books? (source: Google Ngram Viewer )