No matter what kind of transportation you take, there is no specific statement that the toiletries are placed in transparent bottles. If you are flying, you must abide by the 311 principle. Toiletries are placed in a container no larger than 100ml or 3oz.

The emphasis here is that the capacity of the container should not exceed 100ml. Then place the toiletries in 3 to 5 sub-bottles, packed in a transparent bag.