Shatapatha Brahmana 9.1.2.24

9.1.2.24

maṇḍūkena paśūnām | tasmānmaṇḍūkaḥ paśūnāmanupajīvanīyatamo yātayāmā hi so 'vakābhirapāṃ tasmādavakā apāmanupajīvanīyatamā yātayāmnyo hi tā vetasena vanaspatīnāṃ tasmādvetaso vanaspatīnāmanupajīvanīyatamo yātayāmā hi saḥ

With the frog, on the part of animals, whence, of animals, the frog is the one affording least subsistence, for he is used up;--with the lotus-flower, on the part of water, whence of the kinds of water (plants), lotus-flowers are those affording least subsistence, for they are used up;--and with the bamboo-shoot, on the part of trees; whence, of trees, the bamboo is the one affording least subsistence, for it is used up.