Prabhupāda’s small book, Easy Journey to Other Planets, was first published in 1960 in India. (Price: 1 Rupee.) There he asserted that, even on the material platform, the ancient civilization of India had perfected a subtler and more advanced form of space travel through yoga:

"Even if a materialist wants to enjoy developed material facilities, he can transfer himself to the other many many material planets where he can experience more and more advanced material pleasures. The best plan of life is to prepare oneself for going back definitely to the spiritual sky after leaving this body but yet if anyone wants to enjoy the largest amount of material facilities, one can transfer himself in the other planets, not by means of playful sputniks which are simply childish entertainments but by psychological effects (yoga) and learning the art of transferring the soul by mystic powers."

Prabhupāda makes the case that all of this is intended to lead us to achieve the highest, transcendent, eternal planet, Kṛṣṇa-loka.

Prabhupāda’s original booklet had a simple cover, but the illustrated cover of the  first American edition made the comparison between the two kinds of ventures explicit: Easy Journey To Other Planets (by practice of Supreme Yoga).