Garudapurana 1.48.83

1.48.83

hutvā sahasramekaikaṃ devaṃ śirasi kalpayet /
evaṃ madhye tathā pāde pūrṇāhutyā tathā punaḥ //

having offered a thousand [oblations] with each, he should imagine the deity in the head; / likewise in the middle and at the feet, again with a full oblation;