A website dedicated to. . .

. . .the evolution of the toilet was just passed along to me by an Ldotter. The Sulabh International Museum of Toilets

And here you'll find this:

HISTORY OF TOILETS:
The paper presented by Dr. Bindeswar Pathak, Ph.D., D.Litt., Founder, Sulabh Movement at International Symposium on Public Toilets held in Hong Kong on May 25-27, 1995

So, I'm guessing that's what you'd call the definitive toilet paper.