Srimad Bhagavatam Canto 04, Chapter 01, Text 24

SB 4.1.24

pranamya dandavad bhumav
upatasthe ’rhanañjalih
vrsa-hamsa-suparna-sthan
svaih svais cihnais ca cihnitan
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
Thereafter he began to offer prayers to the three deities, who were seated on different carriers — a bull, a swan and Garuda — and who held in their hands a drum, kusa grass and a discus. The sage offered them his respects by falling down like a stick.
 
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
Danda means “a long rod,” and vat means “like.” Before a superior, one has to fall down on the ground just like a stick, and this sort of offering of respect is called dandavat. Atri Rsi offered his respect to the three deities in that way. They were identified by their different carriers and different symbolic representations. In that connection it is stated here that Lord Visnu was sitting on Garuda, a big aquiline bird, and was carrying in His hand a disc, Brahma was sitting on a swan and had in his hand kusa grass, and Lord Siva was sitting on a bull and carrying in his hand a small drum called a damaru. Atri Rsi recognized them by their symbolic representations and different carriers, and thus he offered them prayers and respects.
Srimad Bhagavatam Canto 04, Chapter 01, Text 23
Srimad Bhagavatam Canto 04, Chapter 01, Text 25