這個的確太難了,
《shijin,xiaoya,jiri》:"ji ri gen wu,ji cha wo ma",This meaning It is a good time to go hunting by rid on good moment at lucky day in year of the Horse,this is the example of matching horse with wu.This is the earliest record about 12 Animals.《lunheng,wushi》recorded the same things by Eastern Han Dynasty.
12 animals is a sign for calendar,and is a part of astronomy calendar in ancientry.they have been accepted by people:zi Rat ,chou Ox,yin tiger,mao rabbit,chen dragon,si snake,wu horse,mo Goat,shen monkey,you Rooster,xu dog,hai pig.12 animals relative to each other,and six tunnel return,represents the hope and requirment which ancient want whole Chinese to do.also our ancient hope us to achieve perfection ,without partial,and require us to understand breakthroughing from corresponding point.