Srimad-Bhagavatam: Canto 4 - Chapter 1 - Verse 48
Sanskrit:
मैत्रेय उवाचत आत्मयोगपतय आदिराजेन पूजिता: ।शीलं तदीयं शंसन्त: खेऽभवन्मिषतां नृणाम् ॥ ४८ ॥
ITRANS:
maitreya uvācata ātma-yoga-patayaādi-rājena pūjitāḥśīlaṁ tadīyaṁ śaṁsantaḥkhe ’bhavan miṣatāṁ nṛṇām
Translation:
The great sage Maitreya continued: Being thus worshiped by Mahārāja Pṛthu, the four Kumāras, who were masters of devotional service, became very pleased. Indeed, they appeared in the sky and praised the character of the King, and everyone observed them.
Purport:
It is said that the demigods never touch the surface of the earth. They walk and travel in space only. Like the great sage Nārada, the Kumāras do not require any machine to travel in space. There are also residents of Siddhaloka who can travel in space without machines. Since they can go from one planet to another, they are called siddhas — that is to say, they have acquired all mystic and yogic powers. Such great saintly persons who have attained complete perfection in mystic yoga are not visible in this age on earth because humanity is not worthy of their presence. The Kumāras, however, praised the characteristics of Mahārāja Pṛthu and his great devotional attitude and humility. The Kumāras were greatly satisfied by King Pṛthu’s method of worship. It was by the grace of Mahārāja Pṛthu that the common citizens in his domain could see the Kumāras flying in outer space.