Take part in the whole rite as the Hệ Từ 繫辭 commentary sets it out: hư nhất bất dụng 虛一不用, phân nhị 分二, quải nhất 掛一, thiệt tứ 揲四, quy kỳ 歸奇. The full 18 divisions to one hexagram, with the main, nuclear and resulting hexagrams and the reading of all 64.
The ancients washed their hands, lit incense and spread a cloth before dividing the stalks. Hold one particular matter clearly in mind, one hexagram to one question, and say your invocation in earnest before you begin.
Before there were coins, the ancients divined the Yi with yarrow, the sacred plant that legend says grew on the graves of the sages. The upper Hệ Từ 繫辭 commentary records: the number of the Great Expansion is fifty, of which forty-nine are used. One stalk is set aside unused, called hư nhất bất dụng 虛一不用, standing for the Great Ultimate 太極, unmoving yet giving rise to all things. The remaining forty-nine pass through eighteen divisions, every three making one line, and six lines making a hexagram. This is the slowest and the most solemn method of divination in the Zhou Yi 周易: through all eighteen changes the diviner holds the question single-mindedly in view, and that very slowness is part of the rite.
Each change has four movements that carry the whole cosmology of the Yi. Phân nhị 分二: divide the bundle at random into two handfuls, standing for the Two Forms 兩儀, heaven and earth. Quải nhất 掛一: draw one stalk from the right handful and hold it between the fingers, standing for the human being between heaven and earth, completing the Three Powers 三才. Thiệt tứ 揲四: count each handful four stalks at a time, standing for the turning of the four seasons. Quy kỳ 歸奇: gather the held stalk together with the remainders of both handfuls and set them aside, standing for the intercalary month that makes the year whole. The first change sets aside five or nine stalks; the second and third set aside four or eight. After three changes, the stalks remaining divided by four give six, seven, eight or nine.
| The number after 3 changes | Name | Line | Moving or still | Probability with yarrow | Probability with 3 coins |
|---|---|---|---|---|---|
| 9 | Lão Dương 老陽 | Yang 陽 | Moving, changing into Yin | 3/16 | 2/16 |
| 8 | Thiếu Âm 少陰, the Lesser Yin | Yin 陰 | Still | 7/16 | 6/16 |
| 7 | Thiếu Dương 少陽, the Lesser Yang | Yang 陽 | Still | 5/16 | 6/16 |
| 6 | Lão Âm 老陰 | Yin 陰 | Moving, changing into Yang | 1/16 | 2/16 |
The table shows a subtlety in yarrow that coins do not have: Lão Âm 老陰 comes up three times less often than Lão Dương 老陽, so a moving Yang line appears more readily than a moving Yin line. The ancients held this fitting to the Yi's regard for Yang: Yang is active and so changes easily, Yin is still and so is hard to shift. This page uses the true random division of stalks, and so keeps that classical distribution of probability.
The six lines are built from the bottom upward into the main hexagram, which reflects the present state. The nuclear hexagram takes lines two, three and four as the lower trigram and lines three, four and five as the upper, showing what happens in between. The Lão Âm 老陰 and Lão Dương 老陽 lines change into their opposites to form the resulting hexagram, answering to the final outcome. The rule of Chu Hy 朱熹 for the number of moving lines is applied as well: with one moving line, read that line's text; with several, read the Judgement of the main and the resulting hexagram; with all six moving, use the Dụng Cửu 用九 and Dụng Lục 用六 texts.
By the old ceremony, the diviner washes the hands, dresses properly, lights incense and spreads a cloth, sets the fifty yarrow stalks before them, then makes the invocation, stating name and matter plainly. Throughout the dividing the mind must stay clear, unhurried and silent. One matter takes one hexagram, and it is not cast again in search of a fairer answer. A hexagram is a mirror held up to the times, to show when to advance and when to withdraw. The result is for reflection and guidance; for anything weighty, consult someone qualified to read it deeply.