Sentence:  QUOTE=Do by thy soul, when thou findest it shy of such meditations, as wee do by our horses, that are given to <WSD>boggle</WSD> and start when wee ride them; When they fly back, and start at anything in the way, we do not yield to their fear, and go back (that will make them worse another time) but wee ride them up close to that they are afraid of, and so in time break them of that ill quality. <ref>"Knowledge and practice: or, A plain discourse of the chief things necessary to be known, believ'd, and practised in order to salvation ... The 2d edition revised and inlarged [https://books.google.com/books?id=Tn5mAAAAcAAJ&pg=RA2-PA499] 1665 publisher=William Grantham, Henry Mortlock, and William Miller</ref> 
Meaning of the word marked with <WSD> tags:  Either literally or figuratively to stop or hesitate as if suddenly seeing a bogle.