Here are two citations from one of the links posted in another recent thread on crop circles:
1.)"The storms about this part of_ Surrey have been lately local and violent, and the effects produced in some instances curious. Visiting a neighbour's farm on Wednesday evening (21st), we found a field of_ standing_ wheat considerably knocked about, not as an entirety,_ but in_ patches forming, as viewed from a distance, circular_ spots.
______ Examined more closely, these all presented much the same character, viz., a few standing stalks as a_ centre,_ some prostrate stalks with their heads arranged pretty evenly in a direction forming a circle round the centre, and outside these a circular wall of_ stalks which had not suffered.
____ I send a sketch made on the spot, giving an idea of the most perfect of these patches._ The soil is a sandy loam upon the greensand, and the crop is vigorous, with strong stems, and I could not trace locally any circumstances accounting for the peculiar forms of the patches in the field, nor indicating whether it was wind or rain, or both combined, which had caused them, beyond the general evidence everywhere of heavy rainfall._ They were to me suggestive of some cyclonic wind action, and may perhaps have been noticed elsewhere by some of your readers."
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2.)"Mr William Cyril Williams wrote: "With reference to the corn circles mystery I actually witnessed one being made._ I was standing in a cornfield one morning and saw a whirlwind touching the ground and forming a circle in the corn._ It was just the strength of the wind in the whirlwind that formed the circle".
_ The event happened in the late 1940's when he worked on his father's farm, Penfedw Farm at Cilycwm._ He was then in his twenties._ The area is surrounded by hills on all sides, and circles had been seen there "frequently"._ On this occasion, a weekday in August, at about 10.30 to 11 in the morning [or circa 0930-10 GMT] Mr Williams had gone into the wheat field on harvesting day in advance of the cutting and binding machinery, and was crossing the middle of the field when he heard the buzzing noise of a whirlwind starting up only a few metres away._ He then saw a spinning mass of air with dust in it, and, as he watched, in a matter of_ "only a couple of seconds or so the wheat fell down producing a shard-edged circle 3 to 4 metres in diameter"._ It looked just like the other crop circles he had seen before except that this one was completely flat-bottomed whereas some of the earlier ones had stalks standing at their centres like a conical pyramid._ The vortex then died out rapidly, but during its brief lifetime (under 4 or 5 seconds) it remained at the same place."This page at that site is devoted to promoting the notion that there have aways been non-hoaxed crop circles made by whirlwinds. It mentions that in addition to the two above reports there are about 25 reports of people witnessing whirlwinds producing crop circles.
As far as it goes, I find this to be a very persuasive notion. The two, now famous, original hoaxers who worked for years anonymously fooling people, said they'd been inspired to start by preexisting stories of crop circles. I don't see any reason to look further than whirlwind produced crop circles for the explanation of the stories that were already circulating, and which inspired them to start hoaxing.