It is huge one in a year at most so you shouldn't take risks by using low quality canvas.
Your first two to the above list are extremely important because deep sleep and REM end up being the two most critical stages of sleep. The typically used are lavender and rosemary. https://Www.Streetinsider.com/Press+Releases/Unlocking+The+Body+Begins+Offering+Flotation+Therapy+In+Puyallup/15388647.html