Monday night, Dr. Timothy Leary, former high priest of hallucinogenics who is now at work on a movie about his life, peered out over the hatted Truman Capote to take in the mass of famous faces that filled the dance floor at Studio 54.

"You know, this is not just a birthday party for Liz Taylor," Leary summed up. "This is an esthetic superbowl."

On Feb. 27, in Washington, Elizabeth Taylor Warner turned 46. On Monday night in New York, Halston the designer, and Steve, Rubell, co owner of Studio 54, threw a party for their pal. And a few of their other pals from Irving Lazar to Lauren Bacall to Bianca Jagger to Andy Warhol to make-up wizard Way Bandy, showed up to celebrate.

"I just love Elizabeth," raved Halston, "and that's why I gave this party. If there's any special American royalty, she's it."

Rubell, who called the party "an impromptu thing," thrown together in four days, said he wanted to have it because, "Elizabeth needed an uplift. She's been depressed lately. But she had a wonderful time tonight. She told me it was the best thing that's happened to her in two years."

Husband John Warner left even before the birthday cake arrived around 1 a.m. "Well, John's running for office, you know," said Halston. "So he's putting business before pleasure really."

Taylor, when the moment for the show came, kept her violet eyes glued to the two screens showing scenes from her old movies - all done to the record, something called "Elizabeth."

Following the bits of Taylor's greatest ("Cleopatra" got top audience cheers), the Rockettes - all 44 of them done up in black leotards and silver tap shoes and carrying sparklers - surrounded the cake - decorated by a portrait of Taylor complete with decollette - which had been brought to center floor on a satin-covered platform strewn with gardenias. A flying wedge of bodyguards got Taylor and Halston up to the platform, where she knelt to plunge the knife into the decollete on th cake.

The party was preceeded by a screening of Taylor's latest movie, "A Little Night Music," completed more than six mounths ago, but only now being released because, as producer Elliot Kastner put it, "Nobody wanted it. Err . . . What I mean, is that nobody wanted to pay enough for it."

Guests included lawyer Roy Cohn, Vitas Gerulatis, Marion Javits, who came with Steve Martindale, Eartha Kitt, George Plimpton, Melba Moore, Sylvia Miles, Francesco Scavullo, Margaret Trudeau, Giancardo Giannini, Monique Van Vooren, Diana Vreeland and model-of-the-minute Cheryl Tiegs.

Arriving early - in a horse-drawn carriage - was Truman Capote wearing a pair of monogrammed black velvet slippers (a gift from Frank Sinatra), a black dinner jacket, a bow tie and a necklace - under the bowtie. "This is voodoo bracelet from Martinique," giggled Capote, "and God knows it's exactly what you need in a place like this."

How did Capote view Taylor on her 46th? "Wel," she's a little overweight. But if she lost 20 pounds she'd look great. Apparently, however, it doesn't bother her husband. You know, I've known all her husbands. She's the only girl I know who married every guy she ever slept with. So that's really not so bad, considering that if most girls did that, they'd have been married 50 times before the age of 30."