Asplit infinitive is an infinitive that
a. is used without the word "to."
b. has a word between "to" and the verb.
c. must have a subject.
d. is used as an adjective or a noun.

onto a large boat, and mark the water level that the boat sinks to. then, take the elephant out and put a bunch of marked weights onto the boat until it reaches the same water level. add up the masses of the weights to get the weight of the elephant.