Ilex Guayusa Leaves

Guayusa is unusual. On the one hand, it contains caffeine, and so is useful in
helping to maintain wakefulness. On the other hand, guayusa also contains
an ample supply of L-theanine, an amino acid that imparts a feeling of
pleasant tranquility. The combination of the two creates a light stimulation,
but very smooth. Basically in guayusa you have a stimulant without ragged
edges.

Leaves of Ilex guayusa are used to make an infusion, especially in Ecuador, Peru and Colombia. After harvest, leaves are dried, which allows flavor to develop.

Jivaroan peoples in Ecuador and Peru also prepare a drink from the leaves to be drunk in large amounts during pre-dawn ceremonies that involve the vomiting of the excess drink to wash out the stomach and small intestine and avoid absorbing too much caffeine. A ritual use by the Quechua people involves drinking guayusa infusion to have foretelling dreams for successful hunting expeditions.

Guayusa is also consumed at parties and local festivals as a social drink, especially by the Kichua people in Ecuador.

This information is gathered directly from:
https://en.wikipedia.org/wiki/Ilex_guayusa