Complete Compendium of Five-Star and Three-Fate Astrology, Volume 1

Wood-Rat, Earth-Snake, Earth-Monkey, Wood-Tiger, Metal-Monkey
These five pairs of "Stems and Branches" represent a sample birth chart: Year, Month, Day, Hour, and the Fetal Origin.

For days of Jia and Ji, start the sequence with Jia. For Yi and Geng, Bing is the first. For 丙 Bing and Xin, start from Wu. For Ding and Ren, the sequence resides at Geng-Zi.
From which direction does Gui begin? Ren-Zi Water-Rat is the true path.
For example, if someone is born during the Chou Ox hour on a Jia or Ji day, start from the Zi Rat position with Jia-Zi. Moving forward to the Chou position, the result is Yi-Chou. Follow this logic for all others.
This mnemonic, known as the "Five Rat Mnemonic," is used to determine the Heavenly Stem of the birth hour based on the Heavenly Stem of the birth day.

○ Calculating the Palace of Destiny

Suppose a person is born in the fourth month of a Jia-Zi Wood-Rat year, on a Wu-Shen Earth-Monkey day, during the Yin Tiger hour. According to the formula for Jia and Ji years, the months begin with Bing-Yin; counting to the fourth month, it falls on Si Snake.
For the Si month on a Wu-Shen day, using the formula for Wu and Gui days, the hours begin with Ren-Zi. Counting to the Yin position, one arrives at the Jia-Yin Wood-Tiger hour. Once these four pillars are established, then examine...

...at which month the conception occurred. The method, regardless of gender, is to count forward four signs from the birth month. For example, if the birth month is Ji-Si Earth-Snake, then...
...it lands on Shen Monkey. One then counts back one position from the Wu Horse position to Wei Goat, then calls it Ji-Wei, meaning Geng-Shen Metal-Monkey is the Fetal Origin. This...
The "Fetal Origin" (Taiyuan) represents the time of conception. It is calculated by adding one to the month's Heavenly Stem and three to the month's Earthly Branch.

...is a conception from the seventh month of the previous year. Reaching the fourth month of the following year, the ten-month term is complete, and birth occurs. The Year, Month, Day, Hour, and Fetal Origin are known as the "Five Fates." Once these are established, see in which direction they reside. The method, regardless of gender...

...always begins by placing the first month at the Zi Rat position and counting backward to the birth month. Stop there, then from that position, count forward to meet the birth [hour]...
This describes the initial steps for locating the "Palace of Destiny" (Minggong), a crucial point in a Chinese horoscope representing the individual's core essence.