Murphy's Law applied to the rucksack

No, not RuKsaK, rucksack!

1. No matter how carefully you pack, a rucksack is always too small.
2. No matter how small, a rucksack is always too heavy.
3. No matter how heavy, a rucksack will never contain what you want.
4. No matter what you need, it's always at the bottom.