The Compendium of Caraka 1.5.6

1.5.6

na caivamukte dravye gurulāghavamakāraṇaṃ manyeta, laghūni hi dravyāṇi vāyvagniguṇabahulāni bhavanti; pṛthvīsomaguṇabahulānītarāṇi, tasmāt svaguṇādapi laghūnyagnisandhukṣaṇasvabhāvānyalpadoṣāṇi cocyante 'api sauhityopayuktāni, gurūṇi punarnāgnisandhukṣaṇasvabhāvānyasāmānyāt, ataścātimātraṃ doṣavanti sauhityopayuktānyanyatra vyāyāmāgnibalāt; saiṣā bhavatyagnibalāpekṣiṇī mātrā//

Nor, when this is stated, should one consider heaviness and lightness in a substance to be of no consequence. For light substances abound in the qualities of wind and fire; the others abound in the qualities of earth and water. Therefore, by their own quality too, light substances are of a nature that enkindles the digestive fire and are said to cause little fault even when consumed to satiety. Heavy substances, on the other hand, are not of a nature to enkindle the digestive fire because of their dissimilarity [in qualities]; hence, consumed to satiety, they are excessively faulty, except through the strength of exercise and the digestive fire. This is the measure that depends on the strength of the digestive fire.