A modern study quotes a passage from an ancient work you have not yet opened. The quotation may be exactly what you need for a reading note, but your note should preserve how you encountered it. Otherwise, a useful lead can quietly become a claim of firsthand consultation.
Record both levels of the reference
Write the modern book’s author, title and page, then copy the ancient reference supplied there. Mark the quotation as encountered through that modern source. If a translation is credited, retain that information too.
This is a practical note-taking method rather than a universal citation style. When preparing formal work, follow the required style’s rules for indirect sources. Do not list an edition as personally consulted merely because its name appears in someone else’s footnote.
Check what the surrounding argument adds
Read the paragraph before and after the quotation. Is the modern author using it as evidence, disputing a translation, or presenting a view they later reject? A line extracted from that discussion can acquire a different role when separated from it.
Our article on separating modern commentary from ancient text helps distinguish the voices involved. The same care applies when several authors stand between you and the passage.
Update the note when you reach the source
If you later consult the cited edition, record the new reading separately. Check wording, context and the location of the passage before treating the earlier quotation as verified against it. A different translation may legitimately use different words.
The route matters because another reader should be able to follow it. A modest note saying where you actually read the words is stronger than a polished reference that suggests access you did not have.