The yogi can reduce himself to the size of an atom, or expand

Verse 3.46

ततोऽणिमादिप्रादुर्भावः कायसंपत् तद्धरानभिघात्श्च ॥४६॥

tato-'ṇimādi-prādurbhāvaḥ kāyasaṁpat tad-dharānabhighātśca ॥46॥

From that comes minuteness, and the rest of the powers, “glorification of the body,” and indestructibleness of the bodily qualities.

Verse 3.47

रूपलावण्यबलवज्रसंहननत्वानि कायसंपत् ॥४७॥

rūpa-lāvaṇya-bala-vajra-saṁhananatvāni kāyasaṁpat ॥47॥

The glorifications of the body are beauty, complexion, strength, adamantine hardness.

The yogi can reduce himself to the size of an atom, or expand. He can become light or heavy. He can pierce rocks, have access to everything and master everything.

From samyama on the elements, their counterparts, forms, conjunctions and

fruits, the yogi develops the eight supernatural powers and gains perfect wealth of the body without falling victim to the obstacles posed by the elements. 

This is said to be the best wealth of the body: perfection and freedom from all hindrances.

This sutra indicates that by the conquest of the elements a yogi gains mastery in three fields. The first is the acquirement of the eight supernatural powers. The second is perfection of the body, which means that earth does not soil him, water dampen him, or fire burn him. Wind cannot move him and space can conceal his body anywhere at any time. The third is immunity from the play of the elements and their characteristics, and from the obstructions and disturbances which they create.

The body becomes indestructible; fire cannot injure it. Nothing can injure it. Nothing can destroy it until the Yogi

wishes. “Breaking the rod of time he lives in this universe with his body.” In the Vedas it is written that for that man there is no more disease, death or pain.

PATANJALI YOGA SUTRAS