Skandapurana 1.2.25.12

1.2.25.12

11 atha tasya tejomayaliṃgasyādho'ntaparyantaparicchittaye varāharūpadhāriṇo vipṇoradho lokagamanam, liṃgādhobhāgaśodhanaṃ kṛtvā tasya liṃgasyānantatā niścityaḥ tato nivṛtya punaḥ pūrvasthalaṃ pratyāgamanam ... 245

11. Next, Viṣṇu, assuming the form of a boar, travels to the nether world to ascertain the lower limit of that luminous liṅga; having searched the lower part of the liṅga and determined that the liṅga is infinite, he turns back and returns to his previous place ... 245