You can will changes in your sensory visual experience indirectly, of course, by deliberately looking one direction, or closing your eyes, or pressing on your eyelids. And you can directly will visual imagery experiences by, for example, deciding to form the image of your house as seen from the street. But normally we don't think we can directly will sensory experience: We don't think we can will ourselves simply to see red or see a cross-shaped figure.
In 1894, the eminent psychologist George Ladd asserted, to the contrary, that he and his students could form visual experiences by direct willing.
What they were asked to do was briefly this: to close the eyes, allow the after-images completely to die away, and then persistently and attentively to will that the color-mass caused by the Eigenlicht [that is, the dark or chaotic visual field one supposedly experiences with one's eyes closed] should take some particular form, - a cross being the most experimented with.... Of the sixteen persons experimenting with themselves, four only reported no success; nine had a partial success which seemed to increase with practice and which they considered undoubtedly dependent directly upon volition; and with the remaining three the success was marked and really phenomenal. It should be said, however, that of the four who reported 'no success,' only one appears to have tried the experiment at all persistently.
As far as I am aware no one has ever published an attempted replication of Ladd's experiment.
What do you think? Can you make a cross -- not just an image of a cross but a sensory experience of a cross -- by closing your eyes and trying hard? Ladd recommends a few trials of no more than 5-7 minutes.