'I'm seven and a half exactly.'
'You needn't say "exactually,"' the Queen remarked: 'I can believe it without that. Now I'll give YOU something to believe. I'm just one hundred and one, five months and a day.'
'I can't believe THAT!' said Alice.
'Can't you?' the Queen said in a pitying tone. 'Try again: draw a long breath, and shut your eyes.'
Alice laughed. 'There's no use trying,' she said: 'one CAN'T believe impossible things.'
'I daresay you haven't had much practice,' said the Queen. 'When I was your age, I always did it for half-an-hour a day. Why, sometimes I've believed as many as six impossible things before breakfast. There goes the shawl again!'

Through the Looking Glass (And What Alice Found There), Chapter 5 - Wool and Water