The instruction to "imagine your pelvis is a basin and avoid having the contents spill out by letting it tip" is sometimes used by teachers in an effort to maintain desired alignment of the pelvis. From an anatomical perspective, the directive parallels the concept of a neutral pelvis and avoiding letting the pelvis tilt, particularly in an anterior direction. The problem with this image is that the pelvis is not horizontal but has an angle of inclination. Furthermore, a student who is accustomed to dancing with an anterior pelvic tilt will generally feel that the pelvis is "level." So it is frequently necessary to use tactile or visual cues such as placing the hands on the ASIS and noting when they are vertically aligned relative to the pubic symphysis to identify a neutral position (see Tests and Measurements 4.1, p. 179). Then, the basin or bowl image can often be successfully used to achieve the desired pelvic alignment.
This is an excerpt from Dance Anantomy and Kinesiology.