In the Srimad Bhagavat Purana, Lord Krishna informs Uddhava about numerous mystical powers that can be achieved through yoga. While selected siddhis seem to defy the fundamental laws of physics by giving us the ability to reduce or increase our physical size and mass beyond what we can imagine, others focus on controlling fellow beings, circumstances, or the entire world and on obtaining all objects of our desire. Krishna also discusses lesser yogic powers like freedom from hunger and thirst, mind reading, invincibility, clairvoyance, and the ability to instantly reach a desired destination.
Though Lord Hanuman possessed many such siddhis, his childhood experiences, including a curse from a sage, had taught him to use such powers sparingly — only when needed. Later, due to his sole focus on Rama, the source of all powers, and his wisdom, Hanuman obtained the boon (from Goddess Sita) to bestow any of the siddhis on his devotees at his own discretion.
In contrast, many Indian mystics have enjoyed displaying their petty yogic powers to their followers. A siddhi, unless used unfalteringly for universal benefit, is not a mark of spiritual success. In the absence of bhakti and jnana, it is only a certificate of participation in yoga and may indicate that the seeker has had material desires in his or her mind while meditating. Besides, the enjoyment of controlling nature is not so distinct from being trapped (or controlled) by nature; both are forms of deeper involvement in nature, not attachment to the Supreme Person. So, what is the aim of yoga? Transcending nature, not controlling it. This is why Krishna warns us that siddhis may turn out to be a waste of an advanced-level yogi’s time.