I picked up an old Wired magazine and a subscription card fell out. One one side are the standard "Business reply mail" and "no postage necessary if mailed in the United States" messages.
On the other is a place to write in your name, address, and email to order the magazine. At the bottom of the info section are two checkboxes: "Bill me later" and "Payment enclosed."
I turned that card over and over and still can't see where you can enclose the payment.....