The UN's cultural organisation, Unesco, has formally adopted an extraordinary account of prison life in a Uruguayan jail under military rule.
Written on tiny cigarette papers, it is a diary written by a left-wing guerrilla, Jorge Tiscornia.
He hid the diary for nearly 13 years in the 1970s and 80s in his wooden prison clogs until he was released.
It's been added to Unesco's Memory of the World programme, which rescues historic objects from destruction.
In a statement, Unesco said it was "a living memory of long isolation, revealing the strength of perseverance".
"When you're in a prison cell with no natural light, you don't know what time it is, and after a few days pass you start to lose your sense of what day it is," Mr Tiscornia told AFP news agency.
He started to write the diary which included reflections on prison life and stories of daily events.
"I think it was an attempt to conquer the day-to-day and at the same time not forget what was happening . Those notes were my guide, an anchor for my memory," he said.
Wrapped in nylon
As the issues Mr Tiscornia was exploring in the diary became more sensitive, he decided to hide the journal.
He made himself a pair of wooden clogs, splitting them open and hollowing out a space to keep his writings, folded and wrapped in nylon.
"I used to shower in them." he said.
The journal reached public attention years after he was released in 1985 when another ex-political prisoner made a documentary film about the diary.
It was donated to the archive of the Uruguayan Presidency's Human Rights Secretariat For the Recent Past and then given UNESCO's protection and recognition.