Shatapatha Brahmana 8.7.1.23

8.7.1.23

tā haitā eva saṃyānyaḥ | etadvai devā viśvajyotirbhirevemāṃlokāntsamayuritaścordhvānamutaścārvācastathaivaitadyajamāno viśvajyotirbhirevemāṃlokāntsaṃyātītaścordhvānamutuścārvācaḥ

Now, these (bricks) are indeed stepping-stones, for by means of the Visvagyotis (bricks) the gods then stepped over these worlds, both from hence upwards, and from above downwards: and in like manner does the Sacrificer now, by means of the Visvagyotis, step over these worlds, both from hence upwards, and from above downwards.