“An Historic” vs. “A Historic”

Latin Latin Poetry
1

Perhaps Horace answers us?

… so the aged state
Of words decay, and phrases borne but late
Like tender buds shoot up, and freshly grow.

… ita verborum vetus interit aetas,
Et juvenum ritu florent modo nata, vigentque.

  • Horace, Ars Poetica, 60-61