"Mathematics is the art of accurate reasoning on inaccurately-drawn figures... let that be our motto."

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Would a minute have mattered? No, probably not, although his young son appeared to have a very accurate internal clock. Possibly even 2 minutes would be okay. Three minutes, even. You could go to five minutes, perhaps. But that was just it. If you could go for five minutes, then you'd go to ten, then half an hour, a couple of hours...and not see your son all evening. So that was that. Six o'clock, prompt. Every day. Read to young Sam. No excuses. He'd promised himself that. No excuses. No excuses at all. Once you had a good excuse, you opened the door to bad excuses.

— Terry Pratchett