Osireion

Definition

The Osireion is the cenotaph — a symbolic tomb — built for king Seti I behind his great temple at Abydos (about 1290 BCE). It is best known to historians of astronomy for its ceiling and wall texts: it carries the earliest substantially preserved copy of the *Book of Nut*, the cosmological text built on the body of the sky-goddess Nut, together with a companion "Dramatic Text" and the only ancient Egyptian description of a shadow clock (a device that tells daytime hours by the length of a cast shadow).

In Tradition

Egyptologists treat the Seti I cenotaph at Abydos as one of the key monuments of New Kingdom astronomical religion. Neugebauer and Parker label its *Book of Nut* copy a foundational source, and they use its "birth of Sirius" date as a chronological anchor for dating the Ramesside star clocks. Clagett reproduces its astronomical and cosmological texts in full — the Nut cosmology, the Dramatic Text, and the shadow-clock inscription — as Documents III.12, III.13, and III.16.

In Practice

The Osireion is where several Egyptian sky-traditions survive together in one building. Its arched figure of Nut frames the *Book of Nut*, which sets out how the Sun and the decans (the star-groups that mark the night-hours) are swallowed and reborn along her body. Beside it, the 46-line "Dramatic Text" — first described by Adriaan de Buck in Henri Frankfort's *The Cenotaph of Seti I at Abydos* (1933) — gives a companion cosmological narrative, badly damaged because, like the Shabaka Stone, the ancient copyist worked from an already-defective original. On the roof of the sarcophagus chamber is the only surviving Egyptian technical description of a shadow clock: a 5-palm board with an upright head and crossbar, its hour-marks set at 30, then 12, 9, 6, and 3 units, reversed at noon so the lengthening afternoon shadow measured the remaining hours.

Historical Origin

The cenotaph dates to the reign of Seti I (19th Dynasty, c. 1294-1279 BCE) at Abydos. Its texts were first published by Henri Frankfort, *The Cenotaph of Seti I at Abydos* (London, 1933). They are edited in Neugebauer & Parker, *Egyptian Astronomical Texts* (Vol I, the *Book of Nut*; Vol II, p. 9, the Sirius cross-reference), and reproduced in Clagett, *Ancient Egyptian Science* Vol II (Docs III.12, III.13, and III.16, the shadow clock).

Further Reading

• Marshall Clagett, Ancient Egyptian Science, Volume II: Calendars, Clocks, and Astronomy
• Otto Neugebauer & Richard A. Parker, Egyptian Astronomical Texts, Volume II: The Ramesside Star Clocks