Sentence:  ... in case the Tree be very great ... you must then have a Gin or Crane, such a one as they have to Load Timber with; and by that you may weigh it out of its place, and place the whole upon a <WSD>Trundle</WSD> or Sledge, to convey it to the place you desire; and by the afore-said Engine you may take it off from the <WSD>Trundle</WSD>, and set it in its hole at your pleasure. 
Meaning of the word marked with <WSD> tags:  A low wagon or cart on small wheels, used to transport things.