Both of my parents were cremated. Their wish was to have their ashes mixed together and distributed in the woods on the Blue Ridge Parkway in Virginia, which we did. I was the one who handled the boxes that the cremains came in (each about the size of a double VHS tape plastic container).
The boxes were heavier than I thought that they would be, but still much lighter than their weight at the time of death. @Coloma‘s response would correlate to my personal experience.
What was fascinating in what be considered a morbid sense was that their cremains looked different. Dad’s had small pieces of bone in with the ashes, while Mom’s were just fine ash. I asked a mortician about this, and he said that there were several factors involved. One was that they died 20+ years apart, different funeral homes were used, and that Mom had osteoporosis, all could be a contributing factor.