here we go: Both 1 kilogram of nails and 1 kilogram of feathers have the same weight, which is 1 kilogram.

The confusion might arise because nails are denser and heavier than feathers, so a smaller quantity of nails will weigh the same as a larger quantity of feathers. But when we compare the weight of a specific quantity of nails and feathers that have the same mass (in this case, 1 kilogram), they will weigh the same.