I expressed skepticism, in the first chapter, about the utility of time machines in historical research. I especially advised against graduate students relying on them, because of the limited perspective you tend to get from being plunked down in some particular part of the past, and the danger of not getting back in time for your orals.

The Landscape of History: How Historians Map the Past (ed. Oxford University Press, USA, 2004) - ISBN: 9780195171570