- It is only to be expected that Tannstetter selected different ruling planets for the year in the Latin and French practica for 1513, and predicted entirely different fortunes for those governed by Mercury, because the Latin practica was calculated for Vienna (48 degrees north), while the French one was calculated for Leuven (51 degrees north). Tannstetter was a university-trained astrologer who would have known how to take the different latitutdes into account, and the astrological elections in question are sensitive to changes in location (see J. D. North's Horoscopes and History).
- Although Tannstetter was in Vienna, he composed a practica for Leuven because of an inquiry from there, as the preface to the French practica states: "Car ie suis prest tousiours deu respondre a Louuain ou ailleurs deuant tous maistres qui sentendent a cest faculte." Since he was writing for Leuven rather than Vienna, Tannstetter primarily addressed the fortunes of the Low Countries and neighboring lands, rather than Central Europe.
- The French edition calls itself a translation from the Latin, and it was printed in Geneva, so it's not surprising that some details (like Tannstetter's name) became deformed somewhere along the way.
- The French practica calls its author a "docteur en medicine et en astrologie." The Latin practica for the same year refers to Tannstetter, who had only just begun his studies of medicine, only as "astronomie professor." This may not be an error: according to Franz Stuhlhofer's essential article (“Georg Tannstetter,” Jahrbuch des Vereins für Geschichte der Stadt Wien 37 : 24), Tannstetter advanced to doctor of medicine in May 1513. Midyear is late for the publication of a practica, but if Tannstetter had answered an inquiry after May 11, he could have genuinely given his academic credentials as doctor of both astronomy and medicine. That would make the French practica the earliest printed work to reflect Tannstetter's doctorate in medicine. On the other hand, the French practica includes predictions for the weather beginning in January. There's still something odd about the timeline here.
- In 1523, Tannstetter expressed disdain for Arabic astrologers, preferring instead the Greeks for the foundations of his art. In 1513, however, when the French practica cites Haly and Albumasar, his attitude may not have been so one-sided. His earliest known practica, for 1505, cites as his authority the rules of "Ptholomei Pheludinai, Hali abenragel, Albumasaris, et aliorum in scientia stellarum edoctorum." His practica for 1512 cites Ptolemy, Haly Abenrodan, and Almansor. Disqualifying the French practica based on its citation of Arabic authorities really is an untenable argument.
- Both the French and Latin practicas subdivide human fortunes according to the governing planet. The French practica assigns people in the typical manner according to occupational classes, so that the children of Venus, for examples, are defined as "ieunes galans damoiselles pucelles chantres menestriers danceurs et tous ceulx qui ayment musicque et plaisance." Tannstetter's practicas for 1511, 1519, and 1524 rather unusually subdivide people according to their nativity, while the Latin practicas for 1512 and 1513 do not specify the basis of their subdivision. The different approaches raises serious doubts about the authorship of the French practica, and would be more serious still if not for Tannstetter's practica for 1505, which does assign people to planets by occupational class (including the group, for example, of "Puelle, matrone, cantores, Instrumentorum musicalium pulsatores.")
- What we're left with is a structural argument: Tannstetter's practicas maintain a nearly constant structure from 1505 to 1525, and the French practica does not follow it. The table below compares the organization of the two practicas.
|Latin 1513||French 1513|
|Dedication to Maximilian I|
|1. General configuration of the year||Introduction|
|2. Governing planets||Governing planets|
|3. War and peace||General disposition of the year|
|4. Disease||Winter weather|
|5. Agriculture||Spring weather|
|6. Various regions and cities||Summer weather|
|7. Human fortunes by planet||Autumn weather|
|8. General disposition of the four seasons||Dispositions of the twelve months|
|9. Lunar conjunctions by month||Agricultural fertility and price changes|
|War and peace|
|Human fortunes according to ruling planet|
|Various regions and cities|
In other words, the French practica places Tannstetter's customary final chapters at the beginning of the practica. It's not impossible that a printer could have done that on their own initiative to follow the local style, but it seems unlikely that Tannstetter himself would have done so.
Now that I've gone through it again, I'm somewhat more inclined to see Transtecter as Tannstetter, but with some significant distortions occurring between Vienna and Geneva, and a few other odd things going on. We still can't be sure that the French practica really is Tannstetter's, but it's moving further into the realm of possibility.