In Sprague de Camp’s Lest Darkness Fall (now available freely on-line!), a historian visiting Rome gets shunted from 1939 to 536AD. Besides half-way decent knowledge of Latin, he has what was in his pockets at the time of the transfer:
He strolled up an alley to be out of sight and began going through his pockets. The roll of Italian bank notes would be about as useful as a broken five-cent mousetrap. No, even less; you might be able to fix a mousetrap. A book of American Express traveler’s checks, a Roman street-car transfer, an Illinois driver’s license, a leather case full of keys-all ditto. His pen, pencil, and lighter would be useful as long as ink, leads, and lighter fuel held out. His pocket knife and his watch would undoubtedly fetch good prices, but he wanted to hang onto them as long as he could.
He counted the fistful of small change. There were just twenty coins, beginning with four ten-lire silver cartwheels. They added up to forty-nine lire, eight centesimi, or about five dollars. The silver and bronze should be exchangeable. As for the nickel fifty-centesimo and twenty-centesimo pieces, he’d have to see.
A modern person would be worse off in regard to coinage, as none of the coins in common circulation are silver or copper. PDAs would hold out as long as the battery charge, though the data within might survive much longer.
If a man knew he was going to be whisked back into the past, he would load himself down with all sorts of useful junk in preparation, an encyclopedia, texts on metallurgy, mathematics, and medicine, a slide rule, and so forth. And a gun, with plenty of ammunition.
But Padway had no gun, no encyclopedia, nothing but what an ordinary twentieth-century man carries in his pockets. Oh, a little more, because he’d been traveling at the time: such useful things as the traveler’s checks, a hopelessly anachronistic street map, and his passport. And he had his wits. He’d need them.
Slide rule could be replaced with a solar panel calculator, the rest makes sense. A person getting shunted from modern Rome or even New York City would be unlikely to carry any sidearm at all, though he might have a pocket knife. A person getting time-shunted from Boise or Nashville may well be better prepared, though his chances of finding any civilization in 536AD would be slim indeed.
So assuming you get moved back in time as you are on a typical day, with just the clothes and the contents of your pockets coming along, how would you do? I would assume that language and medical skills would be more important than specific artifacts, but having a few useful gadgets can’t hurt.
