easy as falling off a log vs plain sailing

easy as falling off a log

adj

  • Very easy. 

plain sailing

adj

  • simple, straightforward, or easy 

noun

  • The navigation of waters free from hazards or unfavourable winds. 

  • Something that is simple, straightforward, or easy; something that offers no troubles or difficulties. 

How often have the words easy as falling off a log and plain sailing occurred in a corpus of books? (source: Google Ngram Viewer )