Casting the I Ching
Yarrow Stalk Method
Various methods of yarrow (milfoil) stalk (Achillea millegolium) divination had been developed by the Han era - all apparently based on the brief description provided in section nine of the commentary on the Appended Phrases, Part One, and commented upon by Wang Bi and Han Kangbo. The reasons for various steps in the process are given there. Extant written versions of these methods were critiqued in the twelfth century by Zhi Xi, who then wrote his own account of what he thought the correct method should be. Zhu's composite or reformed method became the standard way of yarrow stalk divination for the rest of the traditional era and is still the one most generally used today.
The casting of a hexagram requires fifty stalks, manipulated in four stages or operations. These four operations are repeated three times to form a line (one operation set), and, since there are six lines, six operation sets are required for the whole process. However, before these operations begin, one stalk is set aside, which leaves forty-nine.
To Complete the First Set:
Operation One:
Take up the forty-nine stalks, and divide them randomly into two bunches, placing them down one beside the other.
Operation Two:
Take one stalk from the right-hand bunch, and place it between the ring finger and little finger of the left hand.
Operation Three:
Grasp the left-hand bunch in the left hand, and, with the right hand, take bundles of four stalks from it until four or fewer stalks remain. Set this remainder aside. Then count off the stalks from the right-hand bunch by fours until four or fewer stalks remain, and set this remainder aside as well.
Operation Four:
Place the remainder from the left-hand bunch between the ring finger and the middle finger and the remainder from the right-hand bunch between the middle finger and index finger of the left hand. The sum of all the stalks now held in the left hand is either 9 or 5 (either 1+4+4, or 1+3+1, or 1+2+2, or 1+1+3). In this first set, the first stalk - held between the ring finger and little finger - is disregarded in counting up the stalks, so the sum is adjusted to either 8 or 4. The result 4 is a single unit and has the numerical value of 3. The result 8 is a double unit and has the numerical value of 2. Therefore, if the sum of the first counting is 9, it counts as 2; and if the sum is 5, it counts as 3.
This completes the first set, and the stalks that make up the sum are now set aside.
The Second and Third Sets:
The second and third sets are identical, the third being performed with the stalks left over after the second set has been completed:
Operation One:
Take up the remaining stalks, and randomly divide them into two bunches, placing the bunches next to each other.
Operation Two:
Take one stalk from the right-hand bunch, and place it between the ring finger and little finger of the left hand.
Operation Three:
Grasp the left-hand bunch in the left hand, and, with the right hand, take bundles of four stalks from it, until four or fewer stalks remain. Set this remainder aside. Then count off the stalks from the right-hand bunch by fours, until four or fewer remain, and set this remainder aside as well.
Operation Four:
Place the remainder from the left-hand bunch between the ring finger and the the middle finger and the remainder from the right-hand bunch between the middle finger and the index finger of the left hand. This time, the sum of the stalks is either 8 or 4 (1+4+3, or 1+3+4, 1+1+2, or 1+2+1); again, an 8 has the value of 2, and a 4 has the value of 3.
It is from the sum of the three values that result from the three sets of operations that a line is formed. If the first set results in a 5 (which becomes a 4, with a value of 3) and the second and third sets each result in a 4 (value 3), the sum value is 9, which defines an "old" yang line - one that is about to change into a yin line and so warrants separate consideration when the hexagram is interpreted. If the first set results in a 9 (which becomes an 8, with a value of 2) and the second and third sets each result in an 8 (value 2), and sum value is 6, which defines an "old" yin line - one that is about to change into a yang line and, again, warrants separate consideration when the hexagram is interpreted. The other possible sum values arrived at by adding the results of the three sets will either be 7 or 8. Sevens result from the following combinations: 9 (i.e., 8, value 2) +8 (value 2) + 4 (value 3); 5 (i.e., 4, value 3) + 8 (value 2) +8 (value 2); 9 (i.e., 8, value 2) +4 (value 3) +8 (value 2). Eights result from these combinations: 9 (i.e., 8, value 2) +4 (value 3) +4 (value 3); 5 (i.e., 4 (value 3) +8 value 2); 5 (i.e., 4, value 3) +8 (value 2) +4 (value 3). A 7 is a "young" yang line, and an 8 is a "young" yin line. Both of these are "at rest" and not about to change, thus they are disregarded when the individual lines of a hexagram are interpreted. One repeats this procedure six times (6x3 sets) to form a hexagram, working from the first line at the bottom to the sixth line at the top.
When a hexagram consists of entirely "new" lines, one should only consider the Judgment, the Commentary on the Judgments, and the Commentary on the images. However, if there are one or more "old" lines in the hexagram, one should consult the Line Statements and the Commentary on the images for such lines. Also, one must consider the "new" hexagram that results from the movement or change of the "old" lines and should consult its Judgment, Commentary on the Judgments, and Commentary on the images.
The Coin Method
Given the complexity of the yarrow stalk method, it was inevitable that some other simpler and easier method of casting a hexagram would develop. Of uncertain time and authorship, such a method did, in fact, come into being - the coin method. This may have had origins in popular culture, for it involves the manipulation of coin money - hardly something that one would expect to come out of an elite literati culture. Traditional Chinese coins were made of bronze, had holes in the middle (so they could be strung together), and an inscription on one side.
The method is very simple. One takes up three coins and throws them down together; each throw forms a hexagram line. The inscribed side of a coin is yin, with a value of 2; the reverse side is yang, with a value of 3. If all three coins turn up yang, the sum value is 9, which defines an "old" yang line; if all are yin, the sum value is 6, which defines an "old" yin line. One yang and two yin result in a 7, a "young" yang line; two yin and a yang result in an 8, a "young" yin line. From this point on, one proceeds as for the yarrow stalk method.