As power objects go, this coiled Aztec rattlesnake is not easily surpassed.

Its forked tongue is divided. So are its allegiances.

The careful carving of its underside, which few Aztecs would have ever seen, allies it to the hidden forces of the underworld.

(At Dumbarton Oaks the snake has been installed above a mirror.)

The round pit in its wedge-shaped head once held burning incense whose rising fumes connect it to the gods who rule the sky.

Earthbound yet celestial, the Dumbarton Oaks reptile is closely tied to time. The 13 rattles on its tail enumerate the 13 months of the Aztecs' ritual calendar. The spiral of its coil suggests the turning of the year.

Like many works of Aztec art, this sculpture (of gray porphyry) is intentionally alarming. When confronted with a hissing snake, monkeys jump instinctively. So do many human beings.

The snake is in Gallery 1 of the pre- Columbian pavilion at Dumbarton Oaks, 1703 32nd St. NW. Scholars believe it was carved shortly before invaders from Spain conquered Aztec Mexico in 1521. The pavilion is open to the public Tuesday through Sunday from 2 to 5 p.m. For information call 202-339-6401. A contribution of $1 per visitor is suggested.