Recently China's leader Xi Jinping took the Constitutional oath of office of China. Five years ago his left hand was on a document (China's constitution?) and his right hand was raised, palm forward, fingers curled but not closed. This year he took the oath again but with his right hand more tightly closed1.
The only other presidential oath to a constitution that I'm familiar with is that in the US, where the president holds the same right arm in a similar way but with the hand palm forward, open and flat (see also).
Question: What are the origins and symbolisms involved in the differences in hand positions2 when leaders are taking oaths to constitutions?
Answers should focus on these two countries but certainly other examples can be referenced.
1It is worth noting that in politics, a closed hand, what those in the West might call a "fist" can have other symbolism(s) in the East, thought I'm not familiar enough to say exactly what those might be.
2Supporting screenshots from the above-linked videos: