(Time Machine Manual t-shirt now on sale at the NeatoShop)
Rhett Allain, a physicist, offers a few items to consider for your packing list. I’ll give you a moment to retrieve your own list so that we can compare notes.
Ready? Okay, Allain suggests that you may wish to bring electrical devices, such as an ebook reader or a electric motorcycle. Just make sure that they can be recharged through some destination time energy source:
An electronic device would be super useful, but you have to charge it. How could you charge a Kindle? I can think of two ways – one of which might be considered cheating. The first way is to build a battery after you go back in time. It wouldn’t be too hard. You just need an acid and two different types of metals (here is an example battery made from pennies). It might be hard to find these materials, but I would suggest the first book on your Kindle be a book called “how to build a battery from scratch”.
What about another method to charge your kindle? What about a solar panel on your Kindle? They actually make such a thing – it’s a Kindle case with a solar panel. Pretty awesome. You could load hundreds of useful books and just keep using the thing. Yes, you might consider this to be “two things”, but once you put the cover on the Kindle it might just count as “one thing”.
I have my own suggestions: bring local money, a detailed map, orienteering equipment, and a crate in which you can keep your property safe for a very long time.
Then travel back in time. Following the approach of David Xanatos from Gargoyles, acquire a coin that is common in your destination time, but extremely rare in your own time. Place that coin in the crate, bury it, and mark the spot carefully on your map.
Next, travel forward in time, dig up your item, and sell it for a fortune.