Many mandalas of the Rig Veda were written about Soma, or Indra drinking Soma: a hallucinogenic drug and also possibly a stimulant. Of the ones I've read so far poem 10.119
says:

"The violent gusts of wind the draughts that I have drunk have lifted me. Have I not drunk the Soma ?
In my grandeur I have surpassed the heaven and all this spacious earth. Have I not drunk the Soma?"
Aha this spacious earth I shall deposit here or there. Have I not drunk the Soma?
In one short moment I will smite the earth in fury here or there. Have I not drunk the Soma?"

One reason the Rig veda interests me is that I have this notion that Indian culture has its roots in a community of people who were much freer and less rigid. Perhaps this is why these people came from outside or at least lived at the edge. As the rig vedins move into mainland India, the Sama and Yajur vedins take over. The sama vedins construct melodic chants to set the rig veda verses to (perhaps these melodies already existed for another language) , then the Yajur vedins set rituals to these chants and poems that are extremely rigid. Every aspect of the ritual alter is closely constructed with utmost attention to geometry (actually requiring many early geometric proofs to be proven by ritualists in the Sulba sutra), linguistics, phonology etc. The rigidity has brought much but probably has also taken away much. The rigid layers are easy to see, I myself am from a family of Yajur vedis. The inspired poets who were high and breathing some fresh mountain air are harder to see.

I learned most of this information by reading Frits Staal and his references.