Matsyapurana 110.6

110.6

gaṅgāyamunayormadhye pṛthivyā jaghanaṃ smṛtam
prayāgaṃ rājaśārdūla kalāṃ nārhati ṣoḍaśīm //

The middle of the waist of the earth is said to be between the Ganges and the Yamunâ and no other tîrthas are even equal to 1/16th of its greatness. It is said by Vâyu (or in Vâyu purâṇa?) that the 31/2 crores of tîrthas of Heaven, Âkâśa and the earth are to be found in the Ganges.—6-7.