Since the nineteenth century, one of the 'hot button' topics within the Catholic liturgical sphere has been the shape of the chasuble. Overall, a lot of ink has been spilt on this subject -- ink that, in my estimation, could have been much better spent elsewhere but I digress. However, one of the good elements that came out of this debate was greater awareness of the history and evolution of chasuble design. Of course, suffice it to say, there is no one "correct" shape of chasuble -- just ask the Eastern churches. What's more, this evolution that saw a trimming back of the ampleness of the chasuble is not unique to the Latin rite.
While I have touched before on this subject before, I recently came across a graphic in Paramentica: Tissus Lyonnais et Art Sacré which excellently shows in a single image the kind of evolution that took place over time:
Now, it must be said that these are not the only shapes that can be found in the history of the Latin rite. Dozens of different shapes can be found in the historical examples we have -- a reminder that unlike modern times, there weren't set universal patterns.
So the question that people naturally might wonder is, why? To gain an insight into the possible answer to that question we need to consider two potential angles: one historical, the other liturgical.
Historically speaking, in earlier centuries textiles were much more rare and precious commodities. Whereas today people are used to having the ability to order bolts of fabric at (relatively speaking) inexpensive prices, throughout most of history that was not the case. Textiles were used and re-used; they were costly and precious, most especially the more beautiful and noble fabrics such as silk. In this regard one had to use what one had. This may have, in part at least, driven design considerations. The maker might have only so much fabric to work with after all.
However, a second consideration is liturgical -- specifically, ceremonial. Practically speaking, ask any contemporary priest what it is like to wear a conical chasuble and they might say "it is heavy" or they might say "it is hot" but in addition to these things, they will also often say that they can be somewhat clunky and impractical, even ceremonially problematic when it comes to performing the liturgical rites. What they mean by this is simply that with so much gathered material, it can become very easy for a priest to do things like knock over items (i.e. the chalice) on the altar while doing things like turning the pages of the missal and so on. This is what in part led to a practice of flipping the arm of the chasuble up over the shoulder -- to get the material out of the way. It wasn't much of a leap at that point to the process of trimming the chasuble shape back in a more permanent way. Indeed, what one will especially note in the evolution of the chasuble design is the gradual trimming back of the excess fabric at the arms, thereby allowing more freedom of movement. (Arguably, one can see a very similar approach in the shape of the Byzantine phelonion -- the effective equivalent of the chasuble).
If we were to watch this evolution in shape take place using a single historical chasuble, it would look something like this:
So it is then that as much as some wish to abstractly speak about 'casula' meaning 'little house' and thus arguing from this that, therefore, the 'best' expressions of the chasuble are the fuller versions, the practical experience of clerics operating within the various rites of the Church has found that the 'little house' in its fullest shape wasn't always as practical as it needed to be to work in harmony with the ceremonial of the rites -- never mind the equally problematic matter of the costliness and scarcity of textiles throughout much of history. What's more, the origins of the chasuble came from the Roman paenula, an everyday garment in Roman society and not one specifically made for the Christian liturgy. In that regard, what we ultimately see in this re-shaping of the casula, of the 'little house' that was the paenula, was the process of making it more fit-for-purpose for the liturgy.
There's a reason, after all, why the conical revival promoted by the early Liturgical Movement has fallen flat each and every time.
