I am looking for any documentation or evidence related to the use of tetrahedral blocks used for torture, specifically forcing the victim to walk, stand or lie on them.
I remember someone presenting the fact that dice, specifically the tetrahedral ones, are explicitly mentioned in the geneva convention as being part of a practice that fell under the category of torture.
I recall asking for evidence of this claim and they did show me something, it was not part of the geneva convention, and it did not refer to them as dice but something like "triangular wooden blocks" but I do recall it being from a reputable source.
Unfortunately I can't find any information about this at all, I am not asking you all to go down a rabbit hole of research, I am hoping that someone who sees this recalls exactly what I am talking about or something related.
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Edit: the document was probably from between 1930 and 1960, probably the 40s.
I believe that what you are referring to is an object called a 'Judas' cradle' (ger. Judaswiege), an alleged torture device resembling high stool with the upper part shaped like a pyramid (either with a triangular or square base). The tortured person was to be either seated on top of it (sometimes with additional weighs attached to the legs) or raised above the device and dropped from a small height, so that the victim was hitting the tip of the pyramid with their perineal area, causing excruciating pain. Now, as is the case of most 'medieval torture devices' with the notable exception of the rack and thumbscrew, the existence of this instrument is not corroborated by any contemporary sources and most depictions were made in 19th century, giving a sound assumption that this torture device is completely fictional.
It may be suspected that the aforementioned device was at least partially influenced by a 'punishment donkey' (ger. Strafesel), sometimes called 'Spanish donkey' per association with Spanish Inquisition, although there is no proof that such a method has ever been used in Spain. The earliest possible mention of the device comes from the French account made in 1646 in Quebec in a description of the punishment for transgressions made by inhabitants of the colony, although the term 'chevalet' (or 'fait mettre sur le chevalet' meaning 'put on chevalet') also appears in 'The Veritable Acts of Martyrs' published in 1732 where it refers to a torture device where some martyrs had their limbs broken, implying a rack-like implement (in modern French the term 'chevalet' means an easel). Nevertheless, this method was quite popular in German lands, primarily as disciplinary measure in the Prussian and army from early 18th century onward. The 'donkey' was a triangular construction resembling gabled rood, sometimes adorned with the wooden head of a horse or donkey. A sentenced soldier was seated on top of it, sometimes additionally encumbered with equipment (weapon, backpack, cannonballs etc.) and forced to remain here for the time prescribed by the rules (usually from one to four hours). Given that this punishment was considered 'light and not painful' (i.e. definitely unpleasant, but not resulting in wounds, unlike, e.g. flogging) we might assume that it was primarily aimed at public shaming and severe discomfort. A derivative punishment was sometimes implemented in some 19th century schools, although the horse (or donkey) was resembling a typical saw-horse and was relatively comfortable to sit on, serving primarily as a separation and shaming device (punished pupil was usually sitting next to the blackboard, facing the class).
Standing on small, sharp objects described in the original post might also refer to the 'post penalty' (ger. Pfhalstrafe, Stäupstrafe), where the person was tied to the post by wrists raised above the head and sometimes was additionally forced to stand on small sharpened sticks that were not inflicting pain by themselves (soldiers were wearing shoes with thick soles, as soldiers receiving 'light' punishments i.e. those not inflicting serious pain were usually fully uniformed and equipped) but made balancing much more difficult and thus adding to the strain of muscles and tendons caused by this uncomfortable position. This was not limited to Germany, as the punishment is evidenced in a steel engraving made by in England William Hogarth (of Rake's Progress fame) in 1720s.
Now, the Geneva Conventions do not mention any particular tortures of painful punishments in detail, as the art. 87 of the Third Geneva Convention relative to the Treatment of Prisoners of War signed on 12th August 1949 states that 'corporal punishments, [...] and, in general, any form of torture or cruelty, are forbidden', so this is very unlikely that any accompanying document would have mentioned particular corporal punishment as they are all deemed unlawful without regard to their character.
Eyler, R.F, Charakter Zuege und historische fragmente an Leben der Koenig von Preussen Friedrich Wilhelm III, Salzwasser Verlag, Paderborn 2011 (reprint of 1843 edition).
Mueller, G.F., Koeniglich-Preussisches Krieges-Recht, Haude und Spener, Berlin 1760.
Ruinart, T. (ed.), de Maupertuy, D. (transl.), Les Veritables Actes des Martyrs, Hippolyte-Louis Guerin, Paris 1732.
Thwaites, R.G. (ed.), Travels and explorations of the Jesuit Missionaries in New France, 1610-1791, vol. XXVIII., The Burrows Brothers, Cleveland 1897.
