[Vigilanteman]

Smart alec! I've done it with a bow and spindle and with a magnifying glass. One of those little cheap sewing kits which you can get at a dollar store or fabric store usually contains a magnifying glass and should be in any man's backpack.

You can also start one with your eyeglasses on a sunny day, which is why you should never leave them on your car's dashboard except in a case.

[Romulus]

Depends on the prescription. Negative diopter prescriptions scatter light and cannot start a fire.

[Telepathic Intruder]

A sandwich and water. I’ve seen it done but haven’t tried it myself. It’s usually when the sun is not out when you need a fire the most, however.