You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Virgil

Context:
The Aeneid appears to have been a great success. Virgil is said to have recited Books 2, 4, and 6 to Augustus; and Book 6 apparently caused Augustus' sister Octavia to faint. Although the truth of this claim is subject to scholarly scepticism, it has served as a basis for later art, such as Jean-Baptiste Wicar's Virgil Reading the Aeneid.

Question:
Which book supposedly caused Augustus' sister to faint?

6