In 1967 the "summer of love" arrived under the influence of hallucinogenic drugs like LSD, magic mushrooms, and marijuana.

The summer of love was the start of the music led flower power philosophy that was spreading around the world. Peace, (free) love and music. Flower children left their parents and their lives back home in search of something better happening somewhere else.

The focus of the psychedelic movement started in the small San Francisco neighborhood of Haight-Ashbury.

The album "Led Zeppelin 4" is technically untitled.
There is no catalogue number, no band name, no title, just a mysterious picture on the cover. The only way to know the contents inside was to buy the album. Led Zeppelin 4 was only identified by 4 symbols symbolizing the identity of each band member. 

With no mention of Zeppelin's name on the album, Jimmy Page insisted that "the music would speak for itself" and the album would be officially titled by the four symbols together.