Gentlemen,
Let me completely disagree
.
The Palm measurement has often varied through time, but allways within the range of 20 cms.
It would correspond, for one, to 1 1/3 of the Roman piede (foot) antico, which messured 294,5 mm, still in use in 1840.
The Wikipedia considers the Palm a mesurement to be taken with the hand fully stretched, measuring around 22 cms.
http://pt.wikipedia.org/wiki/Palmo
The Span ends up measuring about the same, as it corresponds to half Cubit, in which an (ancient Egiptian) Cubit goes from the elbow to the tip of the middle finger.
Apparently the (Egiptian) Cubit is the ancestor of the (Roman) Palm. No doubt that both corespond to the length between the tip of the little finger to the tip of the thumb.
I guess the term Palm is a bit confusing, specially in english, due to being identical to the 'hand palm'.
Is not so ambiguous in (Latin) portuguese as we say palm
o for the measure and palm
a for the hand part.
I believe therefore that the muskets spotted by Tannhauser were indeed much larger than what Michael tends to consider, reason why they were worthy of note.
Also considering the ancient laws that established the legal length of swords, the Palm with 22 cms is the plausible measurement.
King Dom Joćo III, for instance, in his ordination of 1539, defined as within the legal mark, 5 palms for the length of swords, from the pommel to the blade tip; this was about 1,100 mm. These laws were not so much obbeyed, by the way.
Here you will find a contemporaneous converting page, where you can see the measurement of a Portuguese, a Spanish and a Texan Palms.
http://www.onlineconversion.com/length_all.htm
You can also confirm in the page that the span measures about the same.
Fernando