A dark blouse may turn out to be Gai Waterhouse's lucky piece of attire after the trainer's already stellar season reach even greater heights at Scone.

With an unseasonal hot spell catching the always fashion-conscious Waterhouse off guard, the trainer said she was forced give her outfit a run for the second day in a row as she saddled up four runners in Saturday's $400,000 3YO Guineas.

Waterhouse was also wearing the remnants of an errant glass of champagne but it mattered little as she celebrated a Guineas trifecta thanks to Cosmic Endeavour, Liberty's Choice and Ryker.

The result was her latest triumph in a season that has included a breakthrough Melbourne Cup.

The only filly among Waterhouse's quartet, Cosmic Endeavour produced a spirited finish under Kerrin McEvoy, giving the jockey the feature double in successive races after he won the Dark Jewel Classic on Seaside.

Cosmic Endeavour won by a half length from Liberty's Choice with Ryker the same margin away third after being at the front of the field in a strongly run race.

"Cosmic Endeavour was a million to one on the turn but she was strong and she said ' get out my way boys'," was how Waterhouse described the win, her first in the sales-restricted race.

The win helped McEvoy seal the Scone Cup carnival's Golden Whip award as the leading rider over 16 races spread across two days.

"Gai obviously had her in tip-top order and she beat Seaside home at Hawkesbury so there was a good form line there," McEvoy said.

"It was a strong tempo which I thought it would be. She had to do it tough but she gave me plenty over the last two furlongs (400m)."

For trainer Bjorn Baker and Twilight Royale's connections, their hopes of claiming NSW racing's richest pay day with a $2.4 million bonus were never seriously raised.

And Baker said the VRC Sires' Produce Stakes winner's days as a racehorse were more than likely over.

"She is going to the Magic Millions broodmare sale in three weeks," he said.

"After winning half a million dollars and a Group Two she has done a good job.

"Her recent form has been too bad to be true and it was hard to turn it around but we had to have a go."

Sydney jockey Tim Clark claimed riding honours on Guineas day with a winning treble, courtesy of Shigeru Sendan, Atmospherical and Testaryhthm.