Apparently some claimed that the following YinYang, as available in most Chinese medium books, are wrong: -
It seems that whoever has the answer to these 4 items knows the true teaching of Grand-master Yang 楊筠松. I quote, "都天大卦总阴阳，玩水观水有主张，能知山情与水意，配合方可论阴阳。DaoTian DaGua (Celestial City Huge Hexagram) is always about Yin and Yang, it is how it analyzes the water. To understand the affection and meaning of the mountain and water, matching the directions using YinYang. Do you know the relation between Yin Yang and 山情与水意 (passionate mountain with desirous water)?"
I quote again, "有乙辛丁癸之妇，宜配甲庚丙壬之夫，夫夫妇妇，雌雄牝牡。The reason why there is Yi, Xin, Ding, Gui as wives to match Jia, Geng, Bing, Ren as husbands. The husbands and wives, male and female. Do you know why they are considered husband and wife?"
Again, I quote, "甲庚丙壬是阳位。乙辛丁癸是阴位。Do you know what is the rest for 乾坤艮巽 and 寅申巳亥? Why Grand-master Yang 楊筠松 only specify 8? ".
These questions may look simple but the explanation are lengthy... I attempt to answer some.
都天大卦 DaoTian DaGua (Celestial City Huge Hexagram) is the system of Hexagram based on the celestial stars that in ancient time were classified liked an imperial city with the ZiWei or the purple star enclosure as the King's chamber. Not sure what I am talking about, read HERE. Therefore, it is important to understand which part of the Heaven you are measuring if you use XKDG techniques. It divides the Heaven into YinYang.
As above, so below - above has stars, below has mountains. Mountains are formed by the "pull" of the stars and as it displaces, rivers are formed. Yin is born out of Yang. The celestial stars are stationary. They are Yin. The nearest celestial bodies that "moves" like the Sun and the Moon are Yang. These are the 7 governors that influence waves (did I say NaYin?) on earth and thus governs water. Qi is the mother of water.
Mountain and water is itself YinYang. The entire LienShan 连山 talks about mountain being Yang in appearance, Yin in qualities, while the entire GuiChang 归藏 talks about water being Yin in appearance, Yang in qualities. If you look at Gen Gua 艮 ☶ representing mountain, it has more Yin Yao but it takes the gender of Yang. A closer look at Gui Gua 兌 ☱ representing river, it has more Yang Yao but it takes the gender of Yin.
To understand the affection and meaning of the mountain and water 山情与水意, there are 2 aspects to look at. In form, the sentimental flow of water 意 and the nobility of the mountains 情 are the affectionate mountain embracing the water. In formula, mountain and water 山情与水意 matching the directions using YinYang. The key is direction, referring to facing and location, referring to sitting. That is where the understanding of YinYang 24 mountains become crucial. Can FengShui works without the formula but just with forms? My take is - YES!
夫夫妇妇 Husband and Wife is all talking about - formation. Without the formation, there is no 都天大卦 DaoTian DaGua (Celestial City Huge Hexagram). The physical or form aspect, if you don't know read HERE! The formula aspect Dragon is always referring to the male and therefore Yang while the rivers are Yin therefore female. Here is where the normal SanHe and SanYuan clashes, just by this simple and innocent question, "Which is more important, Incoming or Outgoing Qi?"
SanYuan school will just look for the incoming Qi and tap into it 旺. SanHe school will just look into the outgoing Qi 衰 and tap into whatever that is leftover. Such understanding is terribly wrong! Both schools reckoned that in order to know the incoming Qi 旺, you have to identify the outgoing Qi 衰. Furthermore, it is the concubines that arrive first before the emperor. Therefore, formation becomes important.
In the absent of forms, 有乙辛丁癸之妇，宜配甲庚丙壬之夫，are the premise of the HeTu where 甲庚丙壬 are the Yang and 乙辛丁癸 are the Yin. When they come together it is where the 4 formations are born. Based on this premise alone, YangGong 楊筠松 derived its own "BaGua" and set the tone using the idea of the 12 growth phases that is entirely different from the set based on Real Yin Real Yang principle. If you again, cannot understand what Real Yin Real Yang are, read HERE! YangGong 楊筠松 only specify 8 for a reason that there are only 4 structures with its YinYang pairs. He also specify stems for the same reason of HeTu Qi.
By now you would have realized that the 12 growth phases applied to SanHe 4 formations differ greatly from the 12 growth phases applied to Real Yin Real Yang principle 真阴真阳. It is for an undisclosed reason as to why it has to be liked that. The answer is that YangGong 楊筠松 is using HeTu to be his basis. Ironically, most SanHe LuoPan 24 mountain rings are based on Real Yin Real Yang principle 真阴真阳. That is why for a true YangGong practitioner, the YinYang 24 mountain rings are different! If you care to chart out all the possible frames you will also get the answer for the rest of the 16 mountains.
Knowing this is nothing great, if you don't know how to apply it. In fact it is there in Hung HinCheong's book. Click HERE if you want to know. Yet, many still comfortably uses 12 growth phases applied to Real Yin Real Yang principle 真阴真阳 in BaZi reading? In fact, the entire Ru DiYan (入地眼) is based on this Real Yin Real Yang principle 真阴真阳 YinYang 24 mountain rings and it is also the forerunner of our modern day XuanKong DaGua!
SanYuan, in the beginning do not even have the 24 mountains ring. It was adopted much later and its YinYang are entirely different from what we could see today with its Tian YuanLong, Di YuanLong and Ren YuanLong. It has its origin from the SanHe's Human Plate. This is talking about the Huge SanYuan 大三元 embraces all the sub schools of 8 mansions and DaGua 大卦, not to mention QianKun GuoBao (乾坤國寶) or LongMen BaJu (龍門八局).
There are many masters who are not aware about that the Huge SanYuan 大三元 YinYang. All they know and were teaching is how to fly the Flying Star forward backward based on the SanYuan 24 mountains ring's YinYang and it is exactly what has been taught based on the popular Shen's XuanKong Flying star method. Trust me, most of them is still believing it is the only way to do SanYuan.
All SanYuan formulas fall within this structure of YinYang. It shows to say that the YinYang threshold are within the "cross" 十道 and further splits into Old/Young YinYang right up to the 64 hexagram. It fits perfectly well with YangGong 楊筠松 "BaGua" with its basis in HeTu. Therefore its emphasis is on GuaQi or HeTu Qi and it became the fundamental tenets for eight mansions. 一六行龍四九去，三八入脈二七向；1-6 moving dragon 4-9 exiting, 3-8 incoming veins 2-7 facing and this is how the YinYang threshold of 8 mansions are derived from.