Ram Dass, who in the 1960s joined Timothy Leary in promoting psychedelic drugs as the path to inner enlightenment before undergoing a spiritual rebirth he spelled out in the influential book "Be Here Now," died Sunday at home. He was 88.

"With tender hearts we share that Ram Dass (born Richard Alpert) died peacefully at home in Maui on December 22, 2019 surrounded by loved ones," according to his official Instagram account. "He was a guide for thousands seeking to discover or reclaim their spiritual identity beyond or within institutional religion."

Those who knew him or were familiar with his work shared their remembrances on Twitter.

Ram Dass passed from earth a few hours ago. How perfect that he left this plane on the first night of the Festival of Lights. “Be Here Now” shifted my world when I was young, as it did for millions of others. Praise & thanks to a huge & radiant soul. May he be forever blessed. — Marianne Williamson (@marwilliamson) December 23, 2019

Rest In Peace... shinging light. Ram Dass, you will be so missed. thank you for everything you've given us.... pic.twitter.com/zX38hjkFlx — Belinda Carlisle (@belindaofficial) December 23, 2019

my beloved friend ram dass just left his body. we have all been the beneficiaries of his great love and wisdom. i am broken hearted that he is gone.......... and so it is........... pic.twitter.com/hwMOz80ka2 — Joan Halifax (@jhalifax) December 23, 2019

The man who would become a serene, smiling forerunner of the New Age movement and play a leading role in bringing Eastern spirituality to the West grew up as Richard Alpert in a Jewish family in Newton, Massachusetts.

He considered himself an atheist, and after graduating from Tufts University and earning a Ph.D. from Stanford University, was an up-and-coming psychology professor and researcher at Harvard University in the early '60s.

Ram Dass would later describe himself at the time as a driven "anxiety-neurotic" who had an abundance of knowledge but lacked wisdom. Things began to change when Leary joined the Harvard faculty and the two became close friends.

He had been introduced to marijuana in 1955 by his first patient while working as a health services counselor at Stanford University but Leary took him farther with psilocybin, the compound that gives certain mushrooms hallucinogenic qualities. In his first psychedelic experience, "the rug crawled and the picture smiled, all of which delighted me," Ram Dass wrote in "Be Here Now."

American spiritual teacher Baba Ram Dass (Richard Alpert) poses for a portrait at the First Unitarian Church on Jan. 2, 1970 in San Francisco, California. Robert Altman / Getty Images

Ram Dass and Leary wanted to open the mind to a deeper consciousness and conducted experiments that included giving the drug to "jazz musicians and physicists and philosophers and ministers and junkies and graduate students and social scientists." Afterward, they had them fill out questionnaires about their experiences.

Ram Dass said the subjects found bliss, heightened physical senses, accelerated thought processes, a relaxing of biases and hallucinatory experiences, such as seeing God.

Ram Dass and Leary began including the hallucinogenic drug LSD, which like psilocybin was legal at the time, in their experiments but Harvard was upset that they were using students as subjects and fired them in 1963.

The two former professors later moved to a mansion in Millbrook, New York, made available to them by heirs to the fortune of industrialist Andrew Mellon, and continued their experimentation there.

In an effort to avoid the disappointment of "coming down" from a drug experience, Ram Dass said he and five others locked themselves in a building at the estate for three weeks and took LSD every four hours.

"What happened in those three weeks in that house no one would ever believe, including us," he wrote in "Be Here Now," but they were not able to avoid the inevitable return to reality.

In search for a more permanent enlightenment, Ram Dass went to India in 1967.

A guru gave him his new name, which means servant of God, and he returned to the United States with long hair, a beard and instructions from Maharaj-ji to "love everyone and tell the truth." Drugs would no longer be a major factor in Ram Dass' life.

He wrote about his conversion in "Be Here Now," and provided a road map for the burgeoning New Age movement of spirituality.

Apple co-founder Steve Jobs, who used LSD in his younger years, said the book "transformed me and many of my friends" and George Harrison used the title and general philosophy for one of his post-Beatles songs.

"I was a sort of spiritual uncle to a movement — to a consciousness movement bringing the East and West together," Ram Dass told the San Francisco Chronicle in 2004.