Okay, I think I just found another big piece of the puzzle. In 1896, John Denham Parsons published the book The Non-Christian Cross (London: Simpkin, et al.), which appears to have directly influenced the Appendix #162 to the Companion Bible (the NT volumes of which were published after Bullinger's death, according to my sources). In fact, there seems to be a little plagiarism involved; in chapter 1, Parsons wrote:
"Now the Greek word which in Latin versions of the New Testament is translated as crux, and in English versions is rendered as cross, i.e., the word stauros, seems to have, at the beginning of our era, no more meant a cross than the English word stick means a crutch. It is true that a stick may be in the shape of a crutch, and that the stauros to which Jesus was affixed may have been in the shape of a cross. But just as the former is not necessarily a crutch, so the latter was not necessarily a cross. What the ancients used to signify when they used the word stauros, can easily be seen by referring to either the Iliad or the Odyssey. It will there be found to clearly signify an ordinary pole or stake without any cross-bar. And it is as thus signifying a single piece of wood that the word in question is used throughout the old Greek classics....It never means two pieces of timber placed across one another at any angle, but always of one piece alone....There is nothing in the Greek of the New Testament even to imply two pieces of timber" (Parsons, The Non-Christian Cross, from chapter 1, "Was the Stauros of Jesus Cross-Shaped?").
Compare with the discussion in the Companion Bible:
"Our English word 'cross' is the translation of the Latin crux; but the Greek stauros no more means a crux than the word 'stick' means a 'crutch'. Homer uses the word stauros of an ordinary pole or stake, or a single piece of timber. And this is the meaning and usage of the word throughout the Greek classics.... It should be noted, however, that these five references of the Bible to the execution of Jesus as having been carried out by his suspension upon either a tree or a piece of timber set in the ground, in no wise convey the impression that two pieces of wood nailed together in the form of a cross is what is referred to. Moreover, there is not, even in the Greek text of the Gospels, a single intimation in the Bible to the effect that the instrument actually used in the case of Jesus was cross-shaped" (Companion Bible, Appendix #162).
Of course, we don't know if Parsons may have been the author of the Companion Bible piece, but there is a clear literary relationship between the two texts. Parsons' book is also significant because he makes several claims later repeated by the Society. It seems that Parsons was the source of the Society's claim that Livy used crux to mean only "stake":
"It is therefore noteworthy that even this Latin word 'crux,' from which we derive our words 'cross' and 'crucify,' did not in ancient days necessarily mean something cross-shaped, and seems to have had quite another signification as its original meaning. A reference, for instance, to the writings of Livy, will show that in his time the word crux, whatever else it may have meant, signified a single piece of wood or timber; he using it in that sense" (Parsons, The Non-Christian Cross, from chapter 2, "The Evidence of Minucius Felix").
Interestingly, Parsons gives in a footnote a citation of Livy, indicating that he is referring to "Livy, xxviii. 29". But this is the text I quoted earlier in which Livy used palus, not crux, to refer to the instrument: "Bound to a stake (deligati ad palum) they were scouraged and beheaded" (28.29.11). I don't know where Parsons got the mistaken idea that Livy was using the word crux here; the word crux does appear in 28.37, but this relates an altogether different event sometime later by a different individual (the Carthaginian general Mago, whereas 28.29 concerned the Roman general Scipio). So this looks like a mistake made by Parsons that was picked up by the WTS and repeated ad nauseum.
Parsons also quotes Lucian to support his position, tho a different passage than the one cited by the WTS:
The side light thrown upon the question by Lucian is also worth noting. This writer, referring to Jesus, alludes to "That sophist of theirs who was fastened to a skolops;" which word signified a single piece of wood, and not two pieces joined together.
This is a citation from De Morte Peregrini, but what Parsons does not seem to realize is that the verb anaskolopizoó in the text he quotes is the same one used in Lis Consonantium, 12 to refer to the crucifixion of people on a two-beamed stauros.
There are also other dubious statements. Here is an argument from silence that is quite unreasonable:
Had there been any such intimation in the twenty-seven Greek works referring to Jesus, which our Church selected out of a very large number and called the "New Testament," the Greek letter chi, which was cross-shaped, would in the ordinary course have been referred to; and some such term as Katà chiasmon, "like a chi," made use of.
There is no compelling reason to necessarily expect such a comparison; whereas other writings dating to the time when books of the NT were still under composition (such as Barnabas) do compare the stauros to the Greek letter tau.
The author frequently intimates that Constantine played a dominant role in introducing the cross and even claims that crux simplex remained the primary meaning of stauros through the Middle Ages:
Even as late as the Middle Ages, the word stauros seems to have primarily signified a straight piece of wood without a cross-bar.
The author seems to also have no idea that the word crux clearly referred to a two-beamed cross in Plautus and Seneca.
The full text of this book can be found at this website:
http://members.cox.net/srice1/books/parsons/parsons.htm
