Linseed for waterproof fabrics
Linseed oil has a long history in making waterproof fabrics often including tincloth and oil-skin. Tincloth is a extra hard-wearing close woven fabric coated with a blend of linseed oil and beeswax. It is extremely waterproof and hard and was worn by miners of the Alaskan gold rush. More recently oilcloth was extensively used for weather resistant, waterproof clothing in WW1 and WW2.
Tincloth is made by mixing equal parts boiled linseed oil (you can use a raw oil but it will take longer to dry) and beeswax, heating it gently until it melts and combines. You can add a little turpentine to make it thinner and easier to apply. It is then used to coat the canvas by painting it on or dipping it, then the fabric is hung up to dry, preferably with direct sunlight.