Returning to a few posts back for a moment:
I think that it goes from wuji to taiji to yin and yang. The reasoning behind this is that taiji represents the constant interplay between yin & yang -- they haven't separated yet, and do not yet exist as separate concepts or entities that can exist on their own, even temporarily.
In other words, consider each of these (the following) existing as a state at a given moment. Each state describes fewer things than the previous state, eventually leading to a description of one of "the myriad things" (the numerals indicate levels of distinction):
1- wuji state (everything, no distinctions)
2- taiji state (everything, distinctions visible, but always changing, but still conceptualized as "everything" -- the seed of division is planted here)
3- yin only state
3- yang only state
4- yin/yin state (two bars, both broken)
4- yin/yang state
4- yang/yang state
4- yang/yin state
5- kun trigram
5- gen trigram
5+- and so on, through hexagrams, etc.
As for the pre-trigram two-bar states (e.g. yin/yin), I found those described in a book which is not with me right now, but it makes sense to me conceptually. Of course, it's all just a model.