There are several good proposals about the plant ID on f41r of the Voynich Manuscript (Beinecke 408). Ethel Voynich saw Carduus thistle in it, Edith Sherwood chose Wild Marjoram and Steve D. came up with Common Agrimony. So it looks like this one is really tough for folks to agree on.
I will pile on with new proposal - Dill (Anethum Graveolens) - based on illustration in 14th century Arabic Book of Simple Drugs from Dioscorides, the British Museum here . Dill has the ability to fight flatulence - it is the medieval gas pill. This may explain the 'gassy' top cluster of the plant.