My grandmother always had a problem because her kitchen floor was too level for really efficient churning and solved it (as did many people in those days) by putting a bit of wood on the floor under one of the legs of the churn to make it wobble. There were two specific trees which were found to provide the best kind of wood for this purpose, and both of these are called churnwood trees for this reason. This has caused some confusion in botanical circles, so just for the record the proper names are Citronella Moorei and Ehretia Acuminata. And Murray McLeod, oh Doubting Thomas, look it up if you don't believe it.