One of those got laid this morning and of course I wanted to add it in the incubator that I fired up last night

To be sure I was setting it the right way I candled it in a room with no window and couldn't see the air cell at all no matter which way I turned it. The only other thing I could think of was dropping it in a glass of water but ended up just guessing and tossing it in. For future use is there another way?