What it is
It's the oldest way of consulting that we know in detail. You use fifty stalks of yarrow (蓍, shī), a plant held sacred in China; wooden sticks work just as well today. The Great Commentary, one of the Ten Wings, gives the numbers: "the number of the great unfolding is fifty; forty-nine are used." The full procedure followed today was reconstructed by Zhu Xi in the 12th century.
How it works, briefly
- Set one stalk aside; it isn't used.
- Split the forty-nine into two heaps, at random.
- Take one stalk from a heap, count both heaps off by fours and set the remainders aside.
- Repeat twice more with the stalks that are left.
What's left at the end gives a 6, 7, 8 or 9, as in the line values. That's three rounds per line and eighteen for the whole hexagram. It can take twenty or thirty minutes, and the slowness is part of the practice: it gives you time to stay with your question.
Why its odds differ
With yarrow, a 9 (old yang) comes up three times in sixteen and a 6 (old yin) only once. A 7 comes up five times and an 8 seven times. With the three-coin method, 6 and 9 are equally likely. For those who use the stalks, the imbalance makes sense: yang moves more readily than yin.
Step by step in The Yarrow Stalk Method.