The Himalayan form of Buddhism called Vajrayana, which translates as "the diamond path" or "the indestructible way," is asserted by its adherents to be a shortcut to the goal of selfless and eternal unity with the universe.

Shortcut is, of course, a relative term: To be born and then born but once again can cruelly try a charismatic Christian, while a Buddhist may equably endure through a state of grace.

Some sense of how long and how patiently the Buddhist faithful have sought this endless end can be gained from "The Silk Route and the Diamond Path," opening this Friday at the Smithsonian Museum of Natural History. The texts, paintings, wall hangings and statuary average something more than a thousand years in age; yet for all that Varjrayana is a divergent sect, the styles have changed less than have Christian concepts during any given century.

The exhibit's photomurals of the Himalayas suggest another transliteration of Vajrayana: "The Hard Way." The sect developed in monasteries built to serve the Chinese and Indian silk/spice traders and pilgrims who made their way across the Top of the World, almost as remote and forbidding as Antarctica. The mountain passes were ruled by demon-worshipping Tibetan tribes, who were eventually converted to Buddhism but put their own distinctive stamp on it. If interim existences were to be served out in those wild mountains, small wonder that they wanted to speed things up a little.

The history of the region is as tangled as its topography, and Dr. Deborah Klimburg-Salter has accomplished wonders of compression in trying to set the exhibit's more than 130 pieces into context. Those unschooled in Vajrayana Buddhism will find the objects interesting enough in and for themselves; further exploration can be done in the catalogue Klimburg-Salter has written (but for a price: $27).

Visitors will find some of the lighting frustratingly dim. It's necessarily so because many of the cloth and paper objects still exist only because they were hidden in cool, dark, dry caves and cannot withstand direct illumination. On the other hand, the semi-darkness lends an appropriately monasterirair to the Evans Gallery. THE SILK ROUTE AND THE DIAMOND PATH --

Through June 30 at the Smithsonian Museum of Natural History (near the Constitution Avenue entrance). Open 10 to 5:30 (to 7:30 May 28 through Labor Day).