Jaiminīya Upaniṣad Brāhmaṇa 4.2.8

4.2.8

atha yāny aṣṭācatvāriṁśataṃ varṣāṇi tat tṛtīyasavanam
aṣṭācatvāriṁśadakṣarā jagatī
jāgataṃ tṛtīyasavanam /

Now, the forty-eight years that follow are the third pressing. The jagatī [metre] has forty-eight syllables; the third pressing belongs to the jagatī.