"Pluma in lucem."
The shopkeeper smiled and handed over the now almost weightless trunk,
"There you go Mr. Potter. Feather light."
Harry picked it up, smiling in gratitude. Magic was extraordinary.
…
He stared at the trunk, filling it with whatever he could think of, weights of 50kg and heavy potion supplies. But every time he picked it up it was still the same weight.
"I don't understand. How? How?"
Harry paced.
It made no sense.
Magic was magic, there was a certain mystery behind it, but this! Things didn't just become weightless... Charms didn't just happen. There was theory behind the spells, explainable theory.
What did it mean?
…
Harry cackled insanely as he flung the case off the top of the Astronomy Tower. If it didn't make sense then he wasn't going to think about it anymore.
But... instead of falling like normal it... glided down like a feather.
What did it mean?
…
"I've done it! I've done it!"
He shouted, laughing in giddy glee.
He did it.
"It wasn't just magic. No. It was all about gravity. Mass stays the same but weight can change based on gravity. The spell changes the gravity surrounding the object, based on a ratio of the mass inside the object, density, and weight of a feather. Ha ha!"
…
"Papa... Papa are you okay?"
Harry looked down fondly at his six year old daughter.
"What is it sweetie?"
She bit her lip in thoughtfulness before she said,
"I don't... understand. Is Transfiguration permanent or not?"
Harry's brow furrowed,
"Its not."
Her eyes widened,
"But... But... it needs energy to change into one form from the other, the spell, and then... Where does it get the energy to change back?"
He stared.
"Avifors."
The small tennis ball they played catch with earlier changed into a statue of a robin.
…
2 weeks later...
"Papa? It didn't change back."
Harry stared, twitching slightly, at the in tact transfigured statue. What?
He'd never thought it was permanent, since he'd always used the counter spell in the end. Like they were taught.
"Papa?"
Harry turned to his sweet sweet daughter. It didn't matter anyway, just a small bit of theory he must of misunderstood.
"Yes Tulip."
She smiled up at him,
"If transfiguration is permanent then why do people buy clothes or... equipment. Since they could just transfigure it out of leaves or sticks or something. Why do people breed animals when you could make a pig out of a desk, and make a hedgehog out of a pincushion? Why, Papa, why?"
Harry's eye twitched.
He said gruffly,
"I need to go for a walk, sweeties, go find your mother."
…
He didn't return for two weeks, and when he did he was half-starved and covered in mud.
All he could whisper was,
"Ministry conspiracy."
Over and over.
Little Lily Luna his seven year old daughter just patted him on the cheek and said soothingly,
"Its the way of the world. It makes no sense."
Before going to find her mother, who was writing the next issue of the Quibbler, blonde hair flying about like mad as she wrote with her quill.
Permanent Transfiguration: Real or an illusion?
And Lily sighed,
"Adults. Can't live with 'em, can't live without 'em."