The Ars Poetica, by Horace, also known as Epistula ad Pisones, is a treatise on poetry written in the form of a letter, and published around 18 B.C. In it, Horace defines and exemplifies the nature, scope and correct way of writing poetry. This work, inspired by the book of the same name by Aristotle, is one of the most influential in Latin literature, and the source of famous concepts in poetics, such as «in medias res» and «ut pictura poesis». The text itself is a poem in 476 dactilic hexameters.
The Carmen Saeculare, or «Song of the Ages», is a hymn written by Horace in 17 b.C. for the Ludi saeculares of the same year. It is believed that the poem was commissioned by the Emperor Augustus and sung by a choir of young men and women during the opening ceremony of the Games of the Century, a religious celebration that happened in Rome once every saeculum (century). The saeculum was considered to be the maximum length of a human life, which means the Games happened once every generation. The poem was written is nineteen sapphic stanzas, and in an elevated and religious tone. (Summary by Leni)