This was part of my reply to a question on Facebook about the cutting and transporting of tesserae.
If cut tesserae were transported to work sites then what were they transported in and how much was worth cutting? If we take the average size for a Roman tesserae as 10mm (3/8") cube, then it is about 3 grams. 9,000 per square metre that's say 27 kgs per square metre (4 1/4 stone per 3' x 3'). An average man can carry about 25 - 30 kgs, for a manual labourer say, 45 kgs (99lbs). So you're not carrying a huge amount in terms of the surface area of tesserae, and what were the bags made of? Hessian sacking would have to be really strong to take that weight, more likely woven baskets as the ones at the bottom of the Ostia stele seem to show.
As a counter ot this though I have seem a photo of a mosaic recently that had the black and white tesserae larger than the colours, maybe that was pre prepared stock?