The mystic perfections achieved by actually successful yogīs are eight in number. Aṇimā-siddhi refers to the power by which one can become so small that he can enter into a stone. Modern scientific improvements also enable us to enter into stone, because they provide for excavating so many subways, penetrating the hills, etc. So aṇimā-siddhi, the mystic perfection of trying to enter into stone, has also been achieved by material science. Similarly, all of the yoga-siddhis, or perfections, are material arts. For example, in one yoga-siddhi there is development of the power to become so light that one can float in the air or on water. That is also being performed by modern scientists. They are flying in the air, they are floating on the surface of the water, and they are traveling under the water.
After comparing all these mystic yoga-siddhis to materialistic perfections, we find that the materialistic scientists try for the same perfections. So actually there is no difference between mystic perfection and materialistic perfection. A German scholar once said that the so-called yoga perfections had already been achieved by the modern scientists, and so he was not concerned with them. He intelligently went to India to learn how he could understand his eternal relationship with the Supreme Lord by means of bhakti-yoga, devotional service.
Of course, in the categories of mystic perfection there are certain processes which the material scientists have not yet been able to develop. For instance, a mystic yogī can enter into the sun planet simply by using the rays of the sunshine. This perfection is called laghimā. Similarly, a yogī can touch the moon with his finger. Though the modern astronauts go to the moon with the help of spaceships, they undergo many difficulties, whereas a person with mystic perfection can extend his hand and touch the moon with his finger. This siddhi is called prāpti, or acquisition. With this prāpti-siddhi, not only can the perfect mystic yogī touch the moon planet, but he can extend his hand anywhere and take whatever he likes. He may be sitting thousands of miles away from a certain place, and if he likes he can take fruit from a garden there. This is prāpti-siddhi.