Could you be thinking of 'Dan Brown - The Lost Symbol'?
It's not a core theme of the novel but there are similar elements:
a clear box
The “Cube” was a massive windowless box. Every inch of the interior walls and ceiling was covered with a stiff mesh of titanium-coated lead fiber, giving the impression of a giant cage built inside a cement enclosure. Dividers of frosted Plexiglas separated the space into different compartments—a laborator
if enough people wished/believed in something it would have an effect and realising it would change the world as we know it.
From this foundation, Katherine Solomon’s research had vaulted forward, proving that “focused thought” could affect literally anything—the growth rate of plants, the direction that fish swam in a bowl, the manner in which cells divided in a petri dish,
the synchronization of separately automated systems, and the chemical reactions in one’s own body.
Even the crystalline structure of a newly forming solid was rendered mutable by one’s mind;
Katherine had created beautifully symmetrical ice crystals by sending loving thoughts to a glass of water as it froze. Incredibly, the converse was also true: when she sent negative, polluting thoughts to the water, the ice crystals froze in chaotic, fractured forms.
Human thought can literally transform the physical world.
so when he dies they will know how much the human soul weighs
After a few seconds, Peter glanced over at Katherine in apparent confusion.
Wait for it, she thought, redirecting Peter’s gaze to the capsule’s digital display, which still quietly glowed, showing the dead man’s weight.
Then it happened.
When Peter saw it, he jolted backward, almost falling out of his chair. “But . . . that’s . ..” He covered his mouth in shock. “I can’t . . .”
It was seldom that the great Peter Solomon was speechless. Katherine’s reaction had been similar the first few times she saw what had happened.
Moments after the man’s death, the numbers on the scale had decreased suddenly. The man had become lighter immediately after his death. The weight change was minuscule, but it was measurable . . . and the implications were utterly mind-boggling.
Katherine recalled writing in her lab notes with a trembling hand:
“There seems to exist an invisible ‘material’ that exits the human body at the moment of death. It has quantifiable mass which is unimpeded by physical barriers. I must assume it moves in a dimension I cannot yet perceive.”
Note: Here only a young man here tries to ravage the laboratory and not a group of people.