Keeping information safe

What are the bits of knowledge that you feel should be kept safe, written on actual paper in your home, just in case Google or other search engines decide (or are ordered to) suppress them?

I mean stuff like the "formula" for gun powder: 

75% potassium nitrate (KNO3), 15% charcoal, 10% sulfur.

Are there any things of that nature that you have written down just in case?

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