Each time you cast for a line, you get one of four numbers. Each number tells you two things: whether the line is yin or yang, and whether it changes.
| Value | Name | Line | Changes? |
|---|---|---|---|
| 6 | old yin | broken | yes, becomes yang |
| 7 | young yang | solid | no |
| 8 | young yin | broken | no |
| 9 | old yang | solid | yes, becomes yin |
Odd numbers are yang (a yang line) and even numbers are yin (a yin line). The outer values, 6 and 9, give a moving line; the middle ones, 7 and 8, a stable line.
With three coins
The most common convention counts heads as 3 and tails as 2 (some people reverse it; pick one and stick with it). Add up the three coins: three tails make 6, three heads make 9, two tails and a head make 7, and two heads and a tail make 8. The odds are 1/8 for 6, 3/8 for 7, 3/8 for 8 and 1/8 for 9. More in How to Toss the Coins.
With yarrow
The yarrow-stalk method gives different odds: 1/16 for 6, 5/16 for 7, 7/16 for 8 and 3/16 for 9. With this method, old yang comes up three times as often as old yin. We explain it in The Yarrow Stalk Method.
Why these numbers
Tradition ties 9 and 6 to yang and yin in their full form. That's why the classical texts name lines with "nine" and "six," never with seven or eight.