The first Mandala ("book") of the Rigveda has 191 hymns. Together with Mandala 10, it forms the latest part of the Rigveda, its composition likely dating to the Early Iron Age.
Hymn 1.1 is addressed to Agni, arranged so that the name of this god is the first word of the Rigveda. The remaining hymns are mainly addressed to Agni and Indra. Hymns 1.154 to 1.156 are addressed to (the later Hindu god) Vishnu. Verse 1.164.46, part of a hymn to the Vishvadevas, is often quoted as an example of emerging monism or monotheism:
"To what is One, sages give many a title / they call it Agni, Yama, Matarisvan." (trans. Griffith)
The editio princeps of the book is due to Friedrich August Rosen, published posthumously in 1838. It was the earliest edition of a Rigvedic Mandala, predating Max Müller's edition of the entire Rigveda by more than 50 years.