Advice for Time-Travelers

In December 2006, I asked the following question about time travel:

Say you have a time machine and wish to go back to sometime in the past. Now let's say you don't want to arouse suspicion by bringing back some kind of futuristic object... What should you bring with you that would enable you to make the most money in the past? ... What would be cheap today but recognizable and valuable in the past?

I think I have the answer: aluminum. Despite it being the most abundant metallic element in the earth's crust, before the Hall-Héroult process was invented in 1886, it was extremely difficult to extract from its ores. As a result, aluminum was considered a precious metal. As Wikipedia says,

Napoleon III, emperor of France, is reputed to have given a banquet where the most honoured guests were given aluminium utensils, while the other guests had to make do with gold.

So remember, before you step into your time machine to go back into the 19th century, pick up a roll of Reynolds Wrap and remember to toss out the packaging.