As you already mentioned Wouter, NGC 3726 belongs to the very first object in which spirals were detected. I had a chance to catch theses details when I tried to see and sketch all mentioned spirals from Parsons between 1850-1861. With 14.5" the main spirals and dark structures were visible. To my own sketch I add two historical sketches.

sketch 1856-1858
NGC3726Sk2.jpg

sketch 1861
NGC3726Sk1.jpg

sketch, 14.5", 202x, NELM 6m5+, Seeing II
NGC3726.jpg