I thought it could be helpful to demonstrate something about how to hold a Violoncello da Spalla and its playing position. There is not only one way, and for sure, the same was three hundred years ago. Violoncello da Spalla is a world of freedom and experimentation, so feel free to try different ways and experiment. You are welcome to write in the comments about your experience. It will be helpful to others too!
Since October, I have been participating in an experiment by Esther Visser, who teaches how to hold and play the violin without shoulder rest and chin rest. It is a research project for her doctorate at Cambridge. If you are interested and you are a professional player, you can still join: there are two sections, both about playing without a shoulder rest, but one also without a chinrest and one with. You need only ten minutes per day of practice, and you can still play with your usual technique for the rest of the day. If you are interested in participating, click here.
Esther is a violinist and an Alexander Technique teacher: if you are unfamiliar with the Alexander technique, I recommend watching the videos below. If you experience any fatigue (or pain) playing or also doing your daily activities, you may find great benefit from taking some Alexander technique lessons. It will gently teach you to use your body correctly, employing only the necessary muscles. It’s a life-changing experience, but you don’t have to trust me, try yourself!
Here is a beautiful and fun demonstration of the Alexander technique principles: it’s a short video and shows what I tried in my video, but waaaaayyy better!
…and these two introductory videos for a deeper insight
Further readings about Violoncello da Spalla's posture:
About playing posture and how to hold a Violoncello da Spalla