Mind blanking is a full-on fight-or-flight response that occurs during frantic moments when we think of nothing for a moment or two. This mental state shares similarities with mind wandering. While mind-wandering occurs when thoughts unrelated to the current task are brought to the forefront of our attention, no stimuli are brought to mind during a mind blank.
There are 4 states of mind according to thoughts frequency (The hertz (symbol: Hz) is the derived unit of frequency in the International System of Units (SI) and is defined as cycles per one second)
12 to 30 Hz -conscious state.
7.5 to 12 Hz -subconscious state.
4 to 7.5 Hz- light sleep or dream state.
2 to 4 Hz-deep sleep or dreamless sleep.
2 Hz -the person will be a coma.
So scientifically it's not possible to have a blank or thoughtless mind. Actually at 0 Hz person will no longer exist.