"Precious few references have been found in early historical records that point to possible crop circles. Probably the most renowned is the "Mowing Devil" case of 1678, in which a farmer's field was said to have been visited by a devilish entity that trampled the crops down in a circle."
Interesting article; includes some info. about a 1964 incident
http://mysteriousuniverse.org/2012/07/the-mowing-devil-mystery/