A scrap of matting has been thrown out, and the sun happens to land on it. That's the whole scene, and the poem leaves it almost bare. Then comes a single word with a question mark: "Edo?"
Edo is the old name for Tokyo, and it also names a historical period in Japan. The speaker seems to see something in that worn, discarded mat that suggests an older world, maybe the look of woven straw or the feel of a past era. But the question mark matters. The speaker isn't sure. It's a guess, a flicker of association rather than a firm claim.
The mood is quiet and curious. There's a gentle surprise in how a piece of rubbish, just by catching the light, can open up a sense of history. The speaker doesn't explain or lecture. They notice, wonder, and stop, leaving the reader to hold the same small moment of uncertain recognition.