After the fields were plowed, the seed bed had to be prepared.  The better the soil was broken up, the better the crops would grow in the soil.  Early seed beds were prepare by hand with sticks, spades, or rakes.  An implement called a harrow was then used to brake up big clumps of soil.  The early harrows were square shaped with spikes attached to a wooden frame pulled by a horse or ox.  Later the design was changed to triangular, which made it easer to pull though the soil by the horse or ox. 

Modern Day cultivators are very large implements which need large tractors to pull them.