Guy Webster was smoking pot with the Mamas & the Papas in the group’s rented house in Los Angeles in 1966 when he had an idea about how to photograph them for the cover of their debut album.

He told them to head into a bathroom, where all four squeezed, fully clothed, into the tub: John Phillips sat in the foreground, and behind him were Cass Elliot, Denny Doherty and Michelle Phillips, her legs stretched across the others’ laps. (Mr. Doherty told a slightly different story: that they had been hiding from Mr. Webster in the tub.)

“You can see how stoned they were,” Mr. Webster said when he showed the picture to an audience attending an exhibition about his career at the Annenberg Space for Photography in Los Angeles in 2012. But the picture had a flaw: It included the toilet — an image, he said, that would have limited sales of the album, “If You Can Believe Your Eyes and Ears,” in family-oriented chain stores.

“So Lou Adler,” he continued, referring to the producer of the album and the president of Dunhill Records, “came up with the idea that when we put shrink wrap over the album, and put a sticker on it that says, ‘Including “California Dreamin’,” we can sell it at Sears. And when the kids take it off, there’s the toilet.”