Śatapatha Brāhmaṇa ("of a hundred paths") 4.2.1.18

4.2.1.18

tāvapidhāya niṣkrāmataḥ | tira evaināvetatkurutastasmādimau sūryācandramasau prāñcau yantau na kaścana paśyati taupurastātparītyāporṇutaḥ purastāttiṣṭhantau juhuta āvirevaināvetatkurutastasmādimau sūryācandramasau pratyañcau yantau sarva eva paśyati tasmātparāgretaḥ sicyamānaṃ na kaścana paśyati tadu paścātprajāyamānaṃ sarva eva paśyati

They step out (from the altar) after closing the two (cups with their hands): thereby they make them invisible; whence no one sees yonder sun and moon when they go forward (eastwards). Having gone round to the front (of the stake), they uncover (the cups), and offer them while standing in front: thereby they make them visible; whence every one sees yonder sun and moon when they go backwards. Hence also no one sees the seed which is cast forwards, but every one sees what is produced backwards.