Look in the glass.

Ask your sisters.

Consult the librarian of the British Museum.
Look at this umbrella." And he held up that sad but still respectable article.

"Look at it.

For ten mortal years to my certain knowledge you have carried that object under your arm, and I have no sort of doubt that you carried it at the age of eight months, and it never occurred to you to give one wild yell and hurl it like a javelin--thus--" And he sent the umbrella whizzing past the professor's bald head, so that it knocked over a pile of books with a crash and left a vase rocking.
Professor Chadd appeared totally unmoved, with his face still lifted to the lamp and the wrinkle cut in his forehead.
"Your mental processes," he said, "always go a little too fast.