I am assuming it is hand sewn and fragile. I would put an old sheet in the bathtub first under the quilt. I would then fill the tub with warm water to cover the quilt and use a mild soap or quilt soap like retro clean. I would hand agitate it and then allow the water to drain. I would then run in clean water, agitate and let it drain until mist of the water was out. I would then use the sheet to lift the quilt out into a laundry basket. I would then bring it to the washing machine and gently place it around the tub sides and allow the machine to spin the water out. I would then lay it out flat to dry if I had a place big enough. If it was warm enough, I might put it on the sheet outside on the grass.