Yuan Tiangang Bone Weight: Sources, 52 Poems & Calculator

What can we actually verify about Yuan Tiangang and bone weight?

Bone weight is a traditional divination lookup that is traditionally attributed to Yuan Tiangang. The attribution is culturally established, but it is not the same as documented authorship.

The surviving official histories confirm that Yuan Tiangang was a real early-Tang figure known for physiognomy. They do not state that he created the later numerical table that adds year, lunar month, lunar day, and birth-hour values.

This distinction matters because the method is often presented online as a precisely dated Tang invention. The primary records do not support that stronger claim.

What the official histories record

The Old Book of Tang, volume 191 places Yuan Tiangang (袁天纲) in its biographies of technical specialists and says he was especially skilled in physiognomy. It records court and face-reading anecdotes, including the well-known story concerning the young Wu Zetian.

The New Book of Tang, volume 204 also includes Yuan in its technical biographies and preserves related physiognomy material.

These texts establish the historical person and his reputation. They do not document:

• a 2.1-7.2 liang table;
• 52 poems authored by Yuan;
• the modern four-part lookup algorithm;
• a teacher-student relationship with Li Chunfeng;
• co-authorship of the Tui Bei Tu as evidence for this method.

Absence from these biographies does not prove when every later tradition began, but it means authorship should be described as attribution, not fact.

What is the later bone weight method?

The modern form adds four values:

1. sexagenary birth-year weight;
2. lunar birth-month weight;
3. lunar birth-day weight;
4. recorded two-hour birth-period weight.

The total usually falls from 2.1 to 7.2 liang and indexes one of 52 poems. You can inspect every value in the complete bone weight chart, or use the free calculator to convert a recorded Gregorian date and show the four-part breakdown.

Are the 52 poems Tang originals?

We have not found a primary Tang source that identifies the current set of 52 poems as Yuan Tiangang's work. Their present circulation, wording, and table association should therefore be treated as a later textual tradition unless a traceable edition proves otherwise.

That also explains why websites can disagree. Tables may be copied from different modern compilations without edition notes. Our calculator makes a reproducibility claim only: it uses the exact values published in our lookup-table page.

What does historical attribution tell us about accuracy?

Nothing by itself. A tradition can be historically interesting without being empirically predictive. Bone weight remains a traditional cultural interpretation, not a scientifically validated personality, career, relationship, health, or forecasting assessment.

The four-value arithmetic can be checked. The poem cannot establish health, wealth, relationship, career, or future outcomes.

How to verify a result

1. Use the recorded civil birth date and birth hour.
2. Verify the lunar conversion and sexagenary year.
3. Confirm the four values against the same published table.
4. Do not invent noon when the birth hour is unknown.
5. Treat the poem as historical cultural material rather than evidence for a decision.

For interpretation boundaries and common misconceptions, continue to what the bone weight score means. For more calendar-derived detail, the BaZi calculator preserves all four stem-branch pillars, while its interpretations remain a traditional framework.

Frequently asked questions

Why is it still called Yuan Tiangang bone weight?

That is the established popular name and search term. Keeping the name helps users find the tradition; qualifying it as a later attribution prevents the name from being mistaken for verified authorship.

Is Yuan Tiangang described as an astronomer in these biographies?

The cited Yuan entries emphasize physiognomy. Astronomy and calendar work are associated with other figures in the same historical setting, especially Li Chunfeng. The source does not justify transferring those credentials to prove the bone weight table.

Where can I calculate it?

Use the bone weight calculator for the conversion and breakdown, then audit it against the full year, month, day, and hour chart. Read the score explanation before interpreting the poem.