They don't admit solitary confinement is torture right at the top (which is telling), but if you scroll down in the wiki you'll find:
Solitary confinement is considered to be a form of psychological torture with measurable long-term physiological effects when the period of confinement is longer than a few weeks or is continued indefinitely.
So who came up with this wonderful concept? In a plot twist, it turns out it was the polite, well-dressed oatmeal people all along:
Quakers and solitary confinement: We thought it was a good idea. Now we don’t! (CT Mirror 3/17/2021)
Oh well, we all make mistakes, right? The final reveal is that they may not at all be who you thought they were:
The SOCIETY of FRIENDS looks like another JEWISH FRONT (9-page PDF)
The usual caveats accompany the work of "Miles Mathis", but when you dig into the Quakers beyond what's included in the paper, it just looks worse and worse.
What? No, it wasn't.
The Greeks had it. But it is probably a lot older.
Torture of being buried alive had been around for far longer. Slow cooked in the brazen bull. Eaten by insects, like that Indiana Jones shit, head in mud above soldier ant mound. Etc etc.
Which Greek myth is it. Where the royal daughter was locked into solitary confinement underground then the god freed an impregnated.
You're referring to the term solitary confinement simply adapted from monastic practices. Like meditation. Even the Bible 40 days and 40 nights in the desert where Satan tested Jesus or John?
But prisoners were put in the cages, hardly solitary confinement, along roadsides left to die for months, crucified left to die for weeks.
It isn't torture unless other torture is used. It's confinement, and I think you'll find they've been locking people up and torturing them since the dawn of mankind. They often got really inventive in how they'd do it.